Nestable container with uniform stacking features

ABSTRACT

Various embodiments of flanged containers that can be stacked in a nested relationship are disclosed so as to provide uniform spacing between the containers to facilitate reliable denesting thereof. The flanges and/or sidewalls of the containers may be provided with features that facilitate alignment and uniform spacing of the nested containers so that a denesting apparatus can reliably denest the containers. Other containers include sidewalls divided into two sections that serve to stabilize stacked container.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to U.S.provisional application No. 60/518,908, filed Nov. 11, 2003, U.S.provisional application No. 60/564,045, filed Apr. 20, 2004, U.S.provisional application No. 60/564,443, filed Apr. 21, 2004, and U.S.provisional application No. 60/599,892, filed Aug. 9, 2004, all entitled“Nestable Container with Uniform Stacking Features,” the entire contentsof each application being hereby incorporated by reference.

BACKGROUND

1. Technical Field

The technical field relates generally to containers which are pressedinto a predetermined formation with a punch and die, and moreparticularly to containers having desirable denesting characteristics.

2. Related Art

Pressed containers have been used in numerous environments for manyyears, with the containers having a common configuration that allowsnested stacking of the containers. Conventional plates or trays, forexample, may have a downwardly and inwardly converging sidewall that iscontinuous with a flat bottom wall, and with a radially extending rimalong its top edge. This configuration allows pressed plates or trays tobe nested in a stack of trays of the same configuration.

Conventional pressed paperboard trays and plate containers, however,typically do not have uniform rim spacing and/or thickness, which leadsto non-uniform stacking. Non-uniformly stacked containers are difficultto denest, or manually separate, which adds cost and time to use of thecontainers. Other aspects of conventional containers may also hinderdenesting.

It would therefore be desirable to provide a container that is capableof stacking in a nested relationship with other like containers and thatis capable of reliable denesting.

SUMMARY

In accordance with a first embodiment, a pressed container has adownwardly convergent peripheral sidewall connected integrally along alower edge to a base and along a top edge to a peripheral rim thatprojects radially outwardly, and features are incorporated into thecontainer that encourage nested stacking in a substantially uniformspaced relationship.

In one embodiment, the flange is divided into a relatively thickradially inner portion and a relatively thin radially outer portion sothat the thick portion uniformly engages the corresponding thick portionof adjacent containers in a nested stack, and the relatively thinportions of adjacent containers are thereby spaced to facilitatereliable denesting.

In another embodiment, the flange is divided into two portions with anupstanding portion along the radially inner edge of the flange and aradially extending portion along a radially outer portion. Theupstanding portions of containers in a nested stack engage, and therebyseparate, adjacent containers to allow the radially outer portion of theflanges to be uniformly spaced to facilitate reliable denesting.

In still another embodiment, the flange of each container includes aplurality of protrusions on the flange that engage the flange of anadjacent container in a nested stack of containers. The protrusionsprovide spacing of the outer peripheral edge of each flange.

In still other embodiments, a rolled or folded peripheral edge of eachflange increases the effective thickness of the flange so that theremainder of the flanges of adjacent containers in a nested stack arespaced to facilitate reliable denesting. The fold or roll in theperipheral edge of the flange of each container may define a curvedcam-like surface that facilitates separation of the nested containers.

In yet other embodiments, a flange may be formed with a groove ordepression extending along the circumference of the flange. A rolled orfolded peripheral edge may extend from the outer rim of the flange andat least partially underneath the depression to facilitate denesting ofstacked containers and to increase the effective thickness of theflange.

In yet other embodiments, a container may be formed with a multi-angledsidewall. The container sidewall may be formed of a lower sidewallextending from a container base at a first angle, and an upper sidewallextending from a plane parallel to the container base at a second,greater angle. A ridge is defined where the upper and lower sidewallsmeet. The ridge and the multi-angled sidewall may increase thecontainer's resistance to forces applied perpendicular to the containerbase, and thus minimize deformation. Further, the sidewall angles mayminimize lateral movement of individual containers in a stack andprovide enhanced nesting/denesting capabilities.

In an additional embodiment, a method is used to form a paperboardcontainer with a rolled downturned flange. Optionally, the flange caninclude a circumferential depression or groove. The flange of thisembodiment generally includes a downwardly sloping shape to help resistbending and a folded-under rolled section to increase strength and toconvey a perception of a stronger, thicker flange. The presence of agroove increases the flange thickness and aids in the removal ofcontainers from a stack. The groove and flange in combination may alsohelp seal lids to the container.

These and other aspects, features, and details of the present inventioncan be more completely understood by reference to the following detaileddescription of a preferred embodiment, taken in conjunction with thedrawings and from the appended claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an isometric view looking downwardly on the open top of anestable container in accordance with a first embodiment.

FIG. 2 is a section view taken along line 2-2 of FIG. 1.

FIG. 3 is an enlarged fragmentary section taken along line 3-3 of FIG.1.

FIG. 4 is a vertical section of a die set used to form the container ofFIG. 1 with a blank of material from which a container is formedpositioned within the die set.

FIG. 5 is a fragmentary isometric view of an apparatus for denesting astack of nested containers.

FIG. 6 is an enlarged fragmentary section taken along line 6-6 of FIG.5.

FIG. 7 is a vertical section taken through a second embodiment of acontainer.

FIG. 8 is an enlarged fragmentary view of the left side of the containerillustrated in FIG. 7.

FIG. 9 is a vertical section through a die set used for forming thecontainer of FIG. 7 with a blank of material used to form the containerpositioned within the die set.

FIG. 10 is a fragmentary vertical section taken through a denestingapparatus and a stack of containers according the second embodiment.

FIG. 11 is an isometric view looking downwardly toward the open top of acontainer according to a third embodiment.

FIG. 12 is an isometric view of a first variant of the third embodiment.

FIG. 13 is an isometric view of a second variant of the thirdembodiment.

FIG. 14 is an enlarged fragmentary section taken along line 14-14 ofFIG. 11.

FIG. 15 is a fragmentary vertical section taken through an apparatus fordenesting a stack of containers of the type illustrated in FIGS. 11, 12,and 13.

FIG. 16 is a vertical section taken through a die set for forming thecontainer of the third embodiment with a blank of material used to formthe container placed in the die set.

FIG. 17 is a fragmentary vertical section showing one side of acontainer according to a fourth embodiment.

FIG. 18 is a fragmentary vertical section of a device for denesting anested stack of containers of the type shown in FIG. 17.

FIG. 19 is a fragmentary isometric view illustrating a die set forforming the container of the fourth embodiment with a blank of materialused to form the container disposed therein in a precursor form.

FIG. 20 is a fragmentary vertical section similar to FIG. 19 with theflange of the precursor being initially folded from the precursor formof FIG. 19.

FIG. 21 is a vertical section similar to FIGS. 19 and 20 with theprecursor having a folded flange and having been separated from the dieset.

FIG. 22 is a fragmentary vertical section of the precursor formed asshown in FIG. 21 having been positioned in a second die set for rollingthe folded edge of the precursor inwardly.

FIG. 23 is a fragmentary vertical section of the second die set with thefolded edge of the precursor having been rolled inwardly.

FIG. 24 is a fragmentary vertical section through a portion of thecontainer according to a fifth embodiment.

FIG. 25 is a fragmentary vertical section through a denesting apparatusand a stack of nested containers of the type illustrated in FIG. 24.

FIG. 26 is a fragmentary vertical section through a die set for formingthe container of FIG. 24.

FIG. 27 is a fragmentary vertical section of the die set of FIG. 26 in aclosed position.

FIG. 28 is an isometric view of a container according to a sixthembodiment.

FIG. 29 is a cross-sectional view of the container of FIG. 28, takenalong line 29-29 in FIG. 28.

FIG. 30 is an enlarged, cross-sectional view of a flange of thecontainer of FIGS. 28 and 29.

FIG. 31 is a fragmentary vertical section through a denesting apparatusand a stack of nested containers of the type illustrated in FIG. 28.

FIG. 32 is a cross-sectional view of a die set used to form anintermediate tray form from a circular blank.

FIG. 33 is an enlarged, cross-sectional view of a portion of the die setof FIG. 32, specifically showing the portions of the die set used toform a flange of the intermediate tray form.

FIG. 34 is a cross-sectional view of the die set of FIG. 32, with thedie retracted and a plunger extended.

FIG. 35 is another cross-sectional view of the die set of FIG. 32 withthe die, plunger, and punch retracted.

FIG. 36 is a cross-sectional view of a second die set used to form afinal pressed container, similar to that shown in FIG. 28, from anintermediate tray form.

FIG. 37A is a cross-sectional view of the second die set of FIG. 36 in aclosed position.

FIG. 37B is an enlarged view of a flange formation element andprotrusion shown in FIG. 37A, with the second die set in apartially-open position.

FIG. 37C is an enlarged view of the flange formation element andprotrusion of FIG. 37B with the second die set in a closed position.

FIG. 37D is an enlarged view of the flange formation element shown inFIGS. 37B and 37C.

FIG. 38 is a cross-sectional view of the second die set of FIG. 36 witha flange formation element retracted.

FIG. 39 is a cross-sectional view of the second die set of FIG. 36 withthe flange formation element and the die retracted.

FIG. 40 is an enlarged, fragmentary, cross-sectional view of a flangeaccording to a seventh embodiment.

FIG. 41 is an isometric view, looking upwardly, of a flange according toan eighth embodiment.

FIG. 42 is an isometric view of a container according to a ninthembodiment.

FIG. 43 is a cross-sectional view of the container of FIG. 42, takenalong line 43-43 of FIG. 42.

FIG. 44 is an enlarged, cross-sectional view of a flange of thecontainer of FIGS. 42 and 43.

FIG. 45 is a fragmentary vertical section through a denesting apparatusand a stack of nested containers of the type illustrated in FIG. 42.

FIG. 46 is a cross-sectional view of a die set used to form anintermediate container form from a circular blank.

FIG. 47 is an enlarged, cross-sectional view of a portion of the die setof FIG. 46, specifically showing the portions of the die set used toform a flange of the intermediate container form of FIG. 46.

FIG. 48 is a cross-sectional view of the die set of FIG. 46, with thedie retracted and a plunger extended.

FIG. 49 is another cross-sectional view of the die set of FIGS. 46 and48, with the die, plunger, and punch retracted.

FIG. 50 is a cross-sectional view of a second die set used to form afinal pressed container from an intermediate tray form.

FIG. 51A is a cross-sectional view of the second die set of FIG. 50 in aclosed position.

FIG. 51B is an enlarged view of a flange formation element andprotrusion shown in FIG. 51A, with the second die set in apartially-open position.

FIG. 51C is an enlarged view of the flange formation element andprotrusion of FIG. 51B in a closed position.

FIG. 52A is a sectional view of a container according to a tenthembodiment.

FIG. 52B is an enlarged fragmentary section of the flange of thecontainer of FIG. 52A.

FIG. 52C illustrates the flanges of stacked containers according to thetenth embodiment.

FIG. 53A is a sectional view of a container according to an eleventhembodiment.

FIG. 53B is an enlarged fragmentary section of the flange of thecontainer of FIG. 53A.

FIG. 53C illustrates the flanges of stacked containers according to theeleventh embodiment.

FIG. 54A is a sectional view of a container according to a twelfthembodiment.

FIG. 54B is an enlarged fragmentary section of the flange of thecontainer of FIG. 54A.

FIG. 54C illustrates the flanges of stacked containers according to thetwelfth embodiment.

FIG. 55A is a sectional view of a container according to a thirteenthembodiment.

FIG. 55B is an enlarged fragmentary section of the flange of thecontainer of FIG. 55A.

FIG. 55C illustrates the flanges of stacked containers according to thethirteenth embodiment.

FIG. 56 illustrates paperboard compression in a rolled section of aflange.

DETAILED DESCRIPTION

Generally, embodiments of the present invention are stackable,denestable trays, plates or other containers having features thatfacilitate denesting or manual separation of the containers whenstacked. The embodiments described in this specification are generallyreferred to as “containers,” which includes trays, plates, and otherstackable products. The containers are typically formed from paperboard,although alternate embodiments may include containers formed from avariety of other materials. Suitable materials include, for example,microwave susceptor laminated paperboard, dual ovenable coated orlaminated paperboard, acrylic release coated paperboard, and polymerextrusion coated paperboard.

According to the exemplary embodiments, a plurality of similarpaperboard containers can be produced having relatively uniform flangethicknesses and outside diameters. The uniform dimensions provide thepaperboard containers with characteristics generally seen only in metalor possibly plastic injection-molded or thermoformed containers. Forexample, when multiple containers according to the present embodimentsare stacked, the relatively small variations in flange dimensions andsidewall angles minimize tray movement in the X and Y directions, ordirections generally parallel with the bases of the containers. Thesecharacteristics and other characteristics of the present embodimentsalso facilitate denesting, as is described in detail below.

Flange thickness may be enhanced by rolling a segment of paperboardbeneath a flange top surface, dimpling or recessing a section of theflange, or by increasing flange thickness by other methods. Flangewidth, or outside diameter, and thickness may be substantially uniformbetween containers. In one embodiment, flange thickness varies by+/−0.007 inches, and outer diameter varies by +/−0.015 inches.

FIGS. 1-3 illustrate a first embodiment of a container 30 having adownwardly tapering frustoconical sidewall 32 that is integrallycontinuous along its bottom edge with a flat circular bottom wall 34,and along its top edge with a radially outwardly directed horizontalflange 36. The sidewall 32 and the flange 35 have a plurality ofradially directed pleats 38. As will be explained in more detail below,an upper peripheral area 40 of the sidewall 32 is relatively thick incomparison to the remaining lower portion 42 of the sidewall 32 tofacilitate alignment of nested containers of the same construction.Similarly, the flange 36 has a relatively thick radially innerperipheral portion 44 and a relatively thin radially outer peripheralportion 46.

The container 30 may be formed from a flat circular blank (not shown) ofmaterial, such as paperboard, with the circular blank of material havinga plurality of radially directed uniformly spaced score lines formedtherein, with the score lines radiating from the peripheral edge of acentral portion of the blank. During a die-forming process to bedescribed in more detail below, the sidewall 32 and the flange 36 arereduced in radius and correspondingly in surface area, and the scorelines are simultaneously compressed to establish the pleats 38 ofgathered paperboard material.

FIG. 4 is a sectional view of a die set 48 for forming the container 30of FIGS. 1-3. The die set 48 has a forming punch 50 and a forming die52. The forming punch 50 has a generally frustoconical downwardprotrusion 54 conforming in shape to an interior of the container 30.Further, the forming punch 50 has an outwardly projecting shoulder 56having a ring-like recess 58 of generally trapezoidal transverseconfiguration around its innermost edge. A frustoconical wall 60 of theprotrusion 54 has a ring-like recess 62 adjacent to the upper edgethereof so that when the container 30 is formed, the upper portion ofthe sidewall 32 and the radially inner portion of the flange 36 can beof greater thickness than the remainder of the sidewall 32 and theremainder of the flange 36, respectively. The forming punch 50cooperates with the forming die 52 and has a frustoconical recess 64generally conforming in size and shape to the frustoconical protrusion54, along with a flat ring-like shoulder 66 adapted to confront theshoulder 56 of the forming punch 50.

To form a container 30, a circular blank (not shown), such as ofpaperboard and as described above, is positioned so as to be engaged bythe forming punch 50 as the forming punch 50 advances toward the formingdie 52. The blank is thereby forced between the forming punch 50 and theforming die 52 so as to assume the configuration illustrated in FIG. 4.

During the compression stroke of the die set 48, the excess blankmaterial adjacent to the upper portion 40 of the sidewall 32 and theinner portion 44 of the flange 36, which is created due to the reductionin the radius and surface area of the sidewall 32 and the flange 36, isallowed to bulge into the continuous space defined by the recesses inthe protrusion 54 and the shoulder 56 so that the relatively thick zones40 and 44 are formed along the upper portion of the sidewall 32 and theinner portion of the flange 36, respectively. The pleats 38 willnormally extend across the thickened portions of the container 30 intheir passage from the bottom wall 34 to the outer edge of the flange 36along preformed score lines in the blank. In other words, since thepre-scored outer ring-like area of the flat blank of material iselevated during the compression process relative to the flat unscoredcenter portion of the blank material, the radius and surface area ofthat ring-like outer portion is reduced, forcing the material to occupya smaller space. The score lines allow the excess material to be bunchedand squeezed together to form the pleats 38.

FIG. 5 illustrates the container 30 stacked in a nested relationshipwith other like containers 30, along with an apparatus 68 for denestingthe containers 30 from the bottom of the stack. The stack of containers30 is positioned in the apparatus 68 with open ends facing upwardly andpositioned between and retained in a vertical orientation by threevertical tapered guides 70. The guides 70 allow a stack of thecontainers 30 to be deposited in the apparatus 68 and retained in asubstantially vertical orientation. Three guides 70 are illustrated inFIG. 5, but additional guides may be used.

The guides 70 are rotatably mounted on bearings (not seen) in theirlower ends and have a first gear 72 that meshes with a second gear 74.The second gears 74 associated with each guide 70 are operativelyinterconnected with a timing belt 76 so that they rotate in unison. Oneof the second gears 74 is in turn driven by a second timing belt 78 onan attached gear 80 by a drive motor 82 having a drive gear 84 locatedthereon. Accordingly, operation of the motor 82 causes each of thesecond gears 74 to rotate, which in turn rotates the first gears 72 at apredetermined and coordinated rate. The first gears 72 are rotatablymounted on fixed support arms 86 above the upper surfaces of the armsand a denesting screw 88 is secured to a common vertical shaft (notseen) with the first gear 72 for unitary rotation therewith. Thedenesting screw 88 is positioned beneath the support arm 86.

Referring to FIG. 6, the denesting screw 88 has a generally cylindricalmain body 90 and a spiral knife-edge type thread 92 that passes throughapproximately one revolution so that it has an uppermost terminal end 94and a lowermost terminal end 96 vertically spaced but adjacent to eachother. Spaced downwardly from the lowermost terminal end 96 is ahorizontal ring-like support 98 that extends substantially but nottotally around the main body 90 so as to define a gap 99 in thering-like support 98.

In order to denest containers 30 from a stack and to drop the lowermostdenested container 30 onto an underlying conveyor belt 100, or any nextoperational element in the system, the stack is placed in the apparatus68 so that the underside of the flange 36 of the lowermost container 30above the threads 92 engages and is supported on the spiral knife-edgethreads 92 of the guides 70. When the motor 82 turns the apparatus 68,the spiral threads 92 rotate such that the upper terminal end 94 of thespiral thread 92 moves into a gap between the flanges 36 of adjacentnested containers 30 and allows the container on top of the thread 92 tobe lowered as the thread 92 is rotated until it reaches the lowermostend 96 of the thread 92, where the container 30 is allowed to drop ontothe partial ring-like support 98. Further rotation of the denestingapparatus causes the gap or the discontinuous portion 99 of thering-like support 98 to move into alignment with the flange 36 of thecontainer 30 resting thereon and the container 30 is allowed to dropthrough the gap 99 and away from the stack onto the underlying conveyorbelt 100.

The knife-edge thread 92 and the partial ring-like support 98 protrude asufficient distance away from the cylindrical main body 90 so as tosupport a significant portion of the relatively thin outer portion ofthe flange 36 of an associated container 30 for reliable operation ofthe denesting apparatus 68. The relatively thick inner portion 44 of theflange 36 on each container 30 rests upon the relatively thick portion44 of the next adjacent lower flange 36, and also supports the nextadjacent upper flange 36 along the relatively thick portion 44 of thatflange 36. Similarly, the relatively thick upper portion 40 of thesidewall 32 of each container 30 engages the corresponding relativelythick upper portions 40 of the sidewalls 32 of the next adjacent upperand lower containers 30 so that the containers 30 are desirably alignedin a nested stack for later separation.

Due to the thickness of the radially inner portion 44, the relativelythin radially outer portion 46 of the flange 36 is spaced from thecorresponding relatively thin radially outer portion 46 of adjacentcontainers 30 to define uniform gaps of sufficient height to permit theinsertion of the spiral knife-edge 92 so that containers 30 can bereliably removed from the bottom of a stack while supporting theremainder of the stack thereabove. There are several other type ofdenesting devices, for example, which use vacuum cups to denestcontainers from a stack. These devices will also dispense containersmore reliably when they include denesting features according to thepresent embodiments.

FIGS. 7-10 illustrate a second embodiment of a container 102. Referringto FIGS. 7 and 8, the container 102 is similar to the container 30 shownin FIGS. 1 and 2 in that it includes a generally frustoconical sidewall104 that is integrally continuous along its lower edge with a flatcircular bottom wall 106, and along its upper edge with a ring-likeoutwardly directed radial flange 108. Radiating pleats 109 extend acrossthe sidewall 104 and the flange 108. In this embodiment, the sidewall104 is deformed during the forming process to define an annular recess110 in the inner surface of the sidewall 104 that is generally V-shapedin cross section, and a generally V-shaped ring-like protrusion 112 inthe outer surface of the sidewall 104. The flange 108 is defined by aradially inner upstanding wall portion 114 and a radially outer flatradial ring-like portion 116.

FIG. 9 illustrates a forming operation of the container 102 in a die set118. The die set 118 has a forming punch 120 and a forming die 122,wherein the forming punch 120 has a generally frustoconical protrusion124 having a ring-like rib 126 of V-shaped cross section formed in thefrustoconical surface thereof approximately a third of the way up thesidewall 104. An annular shoulder 128 is established in the formingpunch 120 adjacent to the upper edge of the frustoconical surface and arecess 130 is formed in the shoulder 138. The forming die 122 has agenerally frustoconical recess 132 conforming to the protrusion 124, anda ring-like depression 134 of generally V-shaped cross section formed inthe frustoconical wall 136 of the recess 130. The depression 134 isaligned with the ring-like rib 126 on the forming punch 120 when theforming punch 120 and the forming die 122 are in a contiguousconfronting relationship. The forming die 122 has a shoulder 138 alongthe upper edge of the frustoconical recess 132 that is alignable withthe shoulder 128 of the forming punch 120, and a radially outwardprotrusion 140 in the shoulder 138 adapted to matingly protrude into therecess 130 in the forming punch 120. When a blank of material (notshown) from which the container 102 is made is positioned in the die set118, it is deformed into the configuration illustrated in FIGS. 7 and 8.

Referring to FIG. 10, a stack of nested containers 102 of the typeillustrated in FIGS. 7 and 8 is shown in a denesting apparatus 68 whichmay be identical to that previously described in FIGS. 5 and 6. Whenlike containers 102 are stacked, as shown in FIG. 10, the inner wallportion 114 becomes aligned with the corresponding inner wall portion114 of the next adjacent upper and lower containers 102 to support thestack of containers 102 in a nested relationship. In this relationship,the radially outer ring-like portion 116 of each container 102 isthereby separated from the corresponding radially outer ring-likeportion 116 of the next adjacent containers 102. The gap between theradially outer portions 116 of the flanges 108 of adjacent containers102 provides for reliable denesting of the stack. Also, the ring-likeprotrusion 112 engages the inner surface of the sidewall 104 of the nextadjacent lower container 102 so as to establish a uniform spacingbetween the sidewalls 104 of adjacent containers 102 and to establish aneatly aligned vertical stack.

FIGS. 11-16 illustrate variants of a third embodiment of a container 142and a method of making the container. Referring to FIGS. 11-13, thecontainer 142 is similar to the container 30 shown in FIGS. 1-2 in thatit includes a frustoconical sidewall 144 integrally continuous along abottom edge with a circular flat bottom wall 146 and along a top edgewith a ring-like radially outwardly directed flange 148. Radiatingpleats 149 are formed in the sidewall 144 and the flange 148 asdescribed in previous embodiments.

Referring to FIGS. 11-15, with specific reference to FIGS. 14 and 15,the flange 148 of the container 142 includes a plurality ofdeformations, namely convex hemispherical protrusions 150 extending fromthe bottom side of the flange 148, and concave indentations 152 definedin the top of the flange 148. The protrusions 150 separate the flanges148 of adjacent like containers 142 in a nested stack of containers 142.The protrusions 150 are illustrated as generally hemispherical, althoughother shapes may be used. There may be any number of such protrusions,with three being shown in FIG. 13, five in FIG. 12, and four in FIG. 11.

Referring to FIGS. 14 and 15, the protrusions 150 serve as spacers suchthat when one container 142 is nested in an underlying container 142, asillustrated in FIG. 15, the outer periphery of the flanges 148 of theadjacent containers 142 are spaced. In order to avoid having theprotrusion 150 on the undersurface of one flange 148 from being inregistry with a depression in the top surface of the next adjacent lowerflange 148, which would obviate the desired spacing between the flanges148, the protrusions 150 can be established in different numbers on thevarious containers 142 or in various radial or circumferential locationsalong the surface of the flange 148, as is illustrated FIG. 15. Noprotrusion is visible for the uppermost container 142 in FIG. 15 becauseits protrusions are at other angular locations than the locationillustrated. FIG. 15 also shows a denesting apparatus 68 of the typepreviously described where corresponding reference numerals have beenapplied and the operation of the denesting apparatus 68 may be identicalto that previously described.

FIG. 16 illustrates a method of making the container 142 a die set 154.The die set 154 includes a forming punch 156 and a forming die 158. Theforming punch 156 has a plurality of generally hemispherical beads 160and the forming die has a plurality of generally hemispherical recesses162. When a blank of material (not shown) from which the container 142is made is positioned between the forming punch 156 and the forming die158 and the forming punch 156 is advanced into registration with theforming die 158, the blank is compressed into the configurationillustrated in FIG. 14. Other systems for forming protrusions can beemployed.

FIGS. 17-23 illustrate a fourth embodiment of a container 164 and amethod of making the container 164. FIG. 17 is a partial sectional viewof the container 164, which includes a bottom wall 234, a sidewall 236,and a flange 230. The flange 230 has a rolled outer portion 232. Therolled outer portion 232 rolls under at a peripheral edge 235. Therolled outer portion 232 has a curved surface which can function as acam in denesting operations, as illustrated in FIG. 18. The container164 also has radiating pleats 240 formed in the sidewall 236 and in theflange 230 which result from radiating score lines (not shown) in theblank from which the container 164 is formed.

With reference to FIG. 18, a denesting apparatus 68 of the typepreviously described is illustrated with corresponding parts having likereference numerals. A stack of nested containers 164 of the shapeillustrated in FIG. 17 is positioned within the denesting apparatus 68such that the spiral knife-edge blade 92 can be inserted betweencontainers 164 to separate the lowermost container 164 in the stack fromthe next adjacent upper container 164. The curved surface of the rollededge 235 of the uppermost container 164 serves as a cam so that when theknife edge 92 engages the curved surface, the container 164 above theknife edge 92 is lifted to establish a separation between adjacentcontainers.

A method of making the container 164 will now be discussed withreference to FIGS. 19-23. Referring to FIG. 19, a first die set 166includes a forming punch 168 and a forming die 170 with a deformed blankof material from which the container 164 is to be made positionedbetween the forming punch 168 and the forming die 170, and also with theforming punch 168 fully received in the forming die 170. The formingpunch 168 includes a frustoconical protrusion 172 having a circularbottom wall 174, a frustoconical wall 176, and a ring-like shoulder 178around the frustoconical wall 176 which is inclined upwardly andoutwardly. The forming punch 168 also includes a plurality of verticalair passages 180 extending from the top surface 182 of the forming punchto the bottom wall 174, the frustoconical wall 176 and the shoulder 178,so that compressed air can be directed through the passages 180 toassist in ejecting a finished container. A central axial passage 184having an enlarged recessed portion 186 at the bottom end thereofslidably receives a plunger 188. The plunger 188 extends to assist inejecting a finished container 164. In the normal default position of theplunger 188, the bottom surface 190 of the plunger 188 is coplanar withthe bottom wall 174 of the frustoconical protrusion of the forming punch168.

A circular ring-like auxiliary plate 192 is mounted around the punch 168for vertical reciprocating movement independent of the forming punch168. The circular ring-like auxiliary plate 192 has a generallyrectangular cross-sectional configuration with a bottom surface 194being beveled so as to slope upwardly and outwardly at the same angle asthe shoulder 178 of the forming punch 168. In a raised position of theauxiliary plate 192, as shown in FIG. 19, the bottom surface 194 of theauxiliary plate 192 is aligned with the shoulder 178 of the formingpunch and in FIG. 20, the auxiliary plate 192 is shown advanceddownwardly relative to the forming punch 168.

The forming die 170 includes a generally frustoconical recess 196 thatgenerally conforms with the frustoconical protrusion 172 of the formingpunch 168. The forming die 170 further has a ring-like shoulder 198 thatis sloped upwardly and outwardly so as to underlie the shoulder 178 ofthe forming punch 168 and the bottom surface 194 of the auxiliary plate192.

The operation of the die set 166 is best understood with reference toFIGS. 19-21. First, a blank of material from which the container 164 isto be formed is positioned between the forming punch 168. As a result,the auxiliary plate 192 and the underlying forming die 170, where it isdeformed into an initial precursor form. Referring to FIG. 20, theforming punch 168 is raised relative to the forming die 170 whileallowing the auxiliary plate 192 to be shifted downwardly relative tothe forming punch 168 and in doing so, the auxiliary plate 192 folds theoutermost portion of the flange of the precursor product verticallydownwardly to form a flap 200.

Referring to FIG. 21, the precursor form of the container illustrated inFIG. 20 is separated from the forming punch 168 by advancing the plunger188 downwardly. Separation can be assisted by passing compressed airthrough the passages 180 in the forming punch 168.

Referring to FIG. 22, the precursor product in the form illustrated inFIG. 21 is then be placed in a second die set 202. The die set 202 has aforming punch 204 with a frustoconical protrusion 206, a frustoconicalsidewall 210 and a horizontal shoulder 212 having a recess 214 formed inapproximately the inner half of the shoulder 212. The recess 214 has atop wall 216 that is inclined slightly downwardly and outwardly. Theforming die 218 of the die set 202 has a frustoconical recess 220 with acircular flat bottom wall 222. The forming die 218 has a shoulder 224with a raised innermost portion 226 that is sloped slightly downwardlyand outwardly in conformance with the slope of the recess 214 in theshoulder 224 of the forming punch 204. Immediately radially outwardlyfrom the sloped portion 226, the shoulder 224 of the forming die 218 hasa ring-like recess 228 of generally semi-circular transverse crosssection that extends around the entire periphery of the forming die 218with the outer edge of the recess 228 being approximately in alignmentwith the downturned edge of the flange 230 of the precursor product,when the product is positioned within the die set 202.

Referring to FIG. 23, when the forming punch 204 is advanced downwardlytoward the forming die 218, the outer edge of the flange 230 is forcedto roll inwardly along the surface of the ring-like recess 228, therebydefining the rolled outer portion 232 of the container 164.

FIGS. 24-27 illustrate a fifth embodiment of a container 242 and amethod of making the container 242. FIG. 24 is a partial sectional viewof the container 242, and FIG. 25 illustrates a stack of containers 242undergoing a denesting operation. Referring to FIGS. 24 and 25, thecontainer 242 has a frustoconical sidewall 244 which is continuous alonga bottom edge with a flat circular bottom wall 246 and along a top edgewith a radially outwardly directed flange 248. The flange 248 isreverse-folded under itself so as to form a rolled or folded outertubular portion 250 and a flat inner flap 252 that is engaged with theundersurface of the radially inner portion 254 of the flange 248. Theouter rolled edge 285 of the flange 248 is therefore curved and canfunction as a cam during denesting operations.

With reference to FIG. 25, a stack of the containers 242 are shown innested relationship adjacent to a denesting apparatus 68 of a typepreviously described. The component parts of the denesting apparatus 68may be identical to those previously described and have been assignedidentical reference numerals. When the denesting apparatus 68 is used toseparate the lowermost container 242 from the remaining stackthereabove, the knife-edge spiral blade 92 rotates and engages thecurved or rolled surface 285 of a flange 248 which serves as a cam tolift the container 242 below the uppermost container 242 to allow theknife edge 92 to be inserted between the flange 248 of that container242 and the flange 248 of the next adjacent lower container 242. Byfollowing the operation previously described for the denesting apparatus68, the lowermost containers 242 in the stack can be sequentiallyremoved and deposited as desired on an underlying conveyor belt or thelike, as illustrated in FIG. 5.

FIGS. 26 and 27 illustrate a die set 256 for forming the container ofFIG. 24. The die set 256 includes a forming punch 258 and a forming die260. The forming punch 258 has a frustoconical protrusion 262 defining aflat circular bottom wall 264, a frustoconical sidewall 266, and ashoulder 268. The shoulder 268 has an annular recess 270 of generallyrectangular cross-section extending along a radially inner edge of theshoulder 268. The forming die 260 has a generally frustoconical recess272 substantially conforming in size and configuration with thefrustoconical protrusion 262 of the forming punch 258, and has acircular flat shoulder 274 around the recess 272. The shoulder 274 inthe forming die 260 has a ring-like recess 276 formed therein having aradially inward flat portion 278 and a radially outward portion 280 ofgenerally semi-circular cross-sectional configuration. The radiallyouter edge of the semi-circular portion 280 is substantially alignedwith the radially outer edge of the recess 268 in the shoulder of theforming punch 258.

The die set 256 is used to finally form a precursor product 282 ofsubstantially of the same configuration as that illustrated in FIG. 20,except that the downturned flap 284 along the edge of the flange of theprecursor 282 is slightly longer. The precursor product is shown in FIG.26. In FIG. 26, the precursor product is illustrated in a space betweenthe forming punch 258 and the forming die 260 and when the forming punch258 is advanced toward the forming die 260 until they are in registry asshown in FIG. 27. During advancement, the downturned flap 284 around theouter edge of the flange 248 is forced into the recess 276 in theforming die 260 so that it rolls inwardly underneath the radially innerportion 286 of the flange 248. The flap 284 is long enough, however, sothat after forming the initial roll, it extends fully radially inwardlybeneath the upper or radially inner portion 286 of the flange 248. Theradially inner portion 286 of the flange 248 can be received in therecess 270 of the forming punch 258 so that the space between theforming punch 258 and the forming die 260 is as desired for formation ofthe container 242.

FIGS. 28-39 illustrate a sixth embodiment of a pressed container 288 anda method of making the container 288. Referring to FIGS. 28-31, thecontainer 288 includes a flange 290 extending outwardly from theentirety of the container sidewall 292. A depression or groove 294 isformed in the flange 290, at a distance of approximately three-quartersof the width of the flange's top surface 293 from the joinder of theflange 290 and sidewall 296. The groove 294 runs along the circumferenceof the flange 290, and is generally U-shaped in cross-section as seen inFIG. 29. In the present embodiment 288, the groove 294 is approximately0.035 inches deep and 0.05 inches wide. The flange 290 itself is about0.3175 inches wide along its top surface 293, and is divided by thedepression 294 into an inner flange segment 306 and an outer flangesegment 308. The placement of the depression 294 on the surface of theflange 290, the depression thickness or width, and/or the overall flangedimensions can vary in accordance with alternative embodiments.

Referring to FIG. 29, the sidewall 292 is divided into an upper sidewall296 and a lower sidewall 298. The upper sidewall 296 and lower sidewall298 extend at different angles relative to the container base 300, andmeet at a ridge 302. The ridge 302 marks the change in angle from thesharper or steeper angle of the lower sidewall 298 to the less steepangle of the upper sidewall 296. When measured with respect to a planeperpendicular to the base 300, the interior of the lower sidewall 298forms an angle of approximately 19 degrees, while the upper sidewall 296forms an angle of approximately 30 to 31 degrees. These angles generallypermit a certain amount of lateral motion (i.e., motion in the X or Yplanes) to occur when multiple containers 288 are stacked, but mayinhibit large amounts of such motion. Further, such angles facilitatestacking containers 288 in such a manner that the flanges 290 ofadjacent containers 288 abut one another, rather than the sidewalls 292of adjacent containers. The 19 degree slope angle may further permitself-alignment of stacked containers 288, permitting the outer diametersof each container 288 to align in a height dimension. Differentembodiments may use different angles for the upper 296 and lower 298sidewalls. For example, containers of differing calipers, flangethicknesses, diameters or depths may employ different angularmeasurements for the sidewalls 296. In general, the angle between theupper sidewall 296 and the lower sidewall 298 should be at least about 5degrees to ensure proper stacking. An angle of ten degrees or more mayalso be used.

The container 288 may be formed from a blank having score lines whichresult in multiple pleats 289 radially extending from the container'sbottom surface 291 along the sidewall 292. These pleats 289 are similarto those discussed in more detail above with respect to FIG. 1.Approximately 40 to 80 score lines are present on each blank, with 60 to72 score lines preferred in a five-inch outer-diameter container. Theexact number of score lines employed in an embodiment varies with theouter diameter, depth, and shape of the container.

With respect to the angled sidewall 292, the ridge 302 defining thechange in angles between the lower sidewall 298 and the upper sidewall296 adds multiple benefits to the container 288. First, the ridge 302may impart additional structural strength to the container 288. Theridge 302 resists twisting and/or shear stresses applied perpendicularto the bottom surface 300, minimizing deformation that may resulttherefrom. This may be referred to as the “hoop strength” of thecontainer 288. For example, the increased hoop strength of the container288 may enhance the angled sidewall's 292 resistance to pressure appliedby a series of stacked, nested containers 288. Thus, the ridge 302 mayprevent deformation that would otherwise occur in a container 288.

FIG. 30 is an enlarged, fragmentary, cross-sectional view of the flange290 and the upper sidewall 296. A portion 304 of the flange 290 rollsunderneath the flange top surface 293 and at least partially beneath thegroove 294. The rolled portion 304 extends from the flange's outer rimor edge 305 under the outer segment 308, and at least partially alongthe under-surface 310 of the depression 294. The rolled portion 304 mayextend along approximately 40% to 75% of the depression's circumferencebefore terminating, although this distance may vary in alternativeembodiments. For example, in some embodiments, the rolled portion 304may extend along the entirety of the depression's 294 circumference. Therolled portion 304 generally increases the thickness of the flange 290,as discussed below with reference to FIG. 31. In the present embodiment,the flange thickness is approximately 0.075 inches, within a tolerancerange of plus or minus 0.007 inches. Similarly, the flange's outerdiameter is 5.00 inches, within a tolerance range of plus or minus 0.015inches.

The inner surface 312 of the rolled portion 304 abuts the under-surface310 of the depression 294. During forming of the container 288, theinner surface 312 and under-surface 310 may be pressure bonded to oneanother. This may, for example, create a cross-linking of fibers betweenthese paperboard layers of the container 288. The pressure bondgenerally assists in maintaining the curvature of the rolled portion 304by maintaining contact between the rolled portion's inner surface 312and the depression's under-surface 310. This, in turn, prevents theflange 290 from deforming with time or use.

FIG. 31 illustrates a stack of containers 288 in a denesting apparatus68. As shown in FIG. 31, the ridges 302 of the stacked containers 288generally do not abut one another. Specifically, when a first container288 is nested or stacked within a second container 288, the outersurface of the first container's ridge 302 does not abut the innersurface of the second container's ridge 302. Instead, the nestedcontainers 288 contact one another at the flanges 290. This provideslateral stability for a stack of containers 288, permitting containersto self-align and thus facilitating denesting.

The inner surface 312 of the rolled portion 304 and the underside of theouter segment 308 define a void space 316. When the container 288 isviewed from the exterior, the void space 316 is not visible. The voidspace 316 generally increases the overall thickness of the flange 290.

As also shown in FIG. 30, the flange 290 and the upper sidewall 296 meetin a circumferential curved edge 314, rather than forming an angledjunction. The curved edge 314 generally may have a radius ofapproximately 0.045 inches, although this dimension may change inalternate embodiments. The curved edge 314 facilitates a gradual changein angle between the flange 290 and the upper sidewall 296, as well asfacilitating denesting operations. In some embodiments, the curved edge314 may be replaced by a more abrupt, angled transition.

The outer edge of the flange 290 generally defines an angled peripheraledge 305 between the outer flange segment 308 and the rolled portion304. When multiple containers 288 are stacked or nested, the rolledportion 304 of a top container 288 rests upon the top surface 293 of abottom container's flange 290, as shown in FIG. 31. The base of the topcontainer's rolled portion 304 may rest at least partially within thebottom container's depression 294, as shown in FIG. 31. However, theradius of the rolled portion 304 is generally greater than the radius ofthe depression 294. Thus, although the bottom container's depression 294may partially accept the base of the top container's rolled portion 304,the rolled portion 304 nonetheless extends upwardly to space the topcontainer's angled edge 305 from the bottom container's angled edge 305,and increases the overall thickness of the flange 290. The spacingpermits the knife edge 92 of the denesting apparatus 68 to move betweenadjacent containers 288 in order to denest the stacked containers 288.

FIGS. 32-39 illustrate various stages during the process ofmanufacturing the nestable container 288. As with previously-describedembodiments, the present container 288 is manufactured in a two-stageprocess. The first stage is forming, from a circular paperboard blank,an intermediate container 318 having a downturned flange 320 made up ofa downturned portion 322 adjacent to the container sidewall 324 and aperpendicular portion 326 depending from the downturned portion 322. Theintermediate container 318 is shown to best effect in FIG. 35, while theprocess for manufacturing the intermediate container is generally shownin FIGS. 32-35. The circular blank from which the intermediate container318 is formed generally may have a diameter of approximately 6.450 to6.560 inches, and a thickness of 0.01 to 0.045 inches, or morespecifically a thickness of 0.013 to 0.024 inches. The paperboard mayalso include a film or laminate of 0.0005 inches thickness.

Turning now to FIG. 32, a die set 330 for forming the intermediatecontainer 318 is shown in cross-section. Unlike the previously-discusseddie sets 48, 118, 154, 202 and 256, in this embodiment a forming punch332 is located beneath a forming die 334. Essentially, the orientationsof the punch 332 and the die 334 are reversed when compared to die setsdiscussed previously.

The forming punch 332 is seated in the forming die 334, with thepaperboard blank pressed into the intermediate container shape 318. Thepunch 332 has a frustoconical protrusion 336 defining a flat, circulartop wall 338, a generally frustoconical sidewall 340, an angled shoulder342, and an upwardly-extending edge wall 344. The frustoconical sidewall340 is further divided into a first angled sidewall portion 346 andsecond angled sidewall portion 348, which meet at a circumferentialridge point 351. The first and second angled sidewalls 346, 348 extendat different angles from a plane parallel to the top wall 338.Specifically, in the present embodiment the first angled sidewallportion 346 forms approximately a 19 degree angle with the top wall 338,while the second angled sidewall portion 348 extends at approximately 30to 31 degrees from a plane perpendicular to the top wall of the punch332. Other orientations of the die sets are within the scope of theinvention.

The angled shoulder 342 of the punch 332 angles slightly towards the topwall 338, and abuts the second angled sidewall 348. The edge wall 344extends upwardly and defines an outer shoulder 342. As described in moredetail below, the angled shoulder 342 and the edge wall 344 combine witha mating surface on the die 334 to form the downturned portion 322 and aperpendicular portion 326 of the intermediate container 318.

The die 334 includes a flat, circular top wall 350, a generallyfrustoconical, downwardly-extending sidewall 352 composed of a first diesidewall 354 and second die sidewall 356, an upwardly angled dieshoulder 358, and upwardly-extending die edge wall 360. As discussedwith respect to the punch 332, the first and second die sidewalls 354,356 extend at different angles and meet at a die ridge 361 extendingalong the circumference of the die 334. The first die sidewall 354extends from the top wall 350 at approximately a 19 degree angle, whilethe second die sidewall 356 extends from the ridge at approximately a30.8 degree angle, measured with respect to a plane perpendicular to thetop wall 350.

The exemplary process of manufacturing the intermediate container 318will now be described with respect to FIGS. 32-35. FIG. 33 depicts withparticularity certain elements of the die 334 and the punch 332. First,a circular blank (not shown) is inserted between the punch 332 and die334, while the die set 330 is open. The blank generally seats in theflat, circular ridge 362 atop the punch 332. Once the blank is seated,the die 334 is lowered onto the punch 332, bending, compressing, anddeforming the paperboard blank to form the intermediate container 318shown in FIG. 32. As the die set 330 closes, the complementary surfacesof the die 334 and the punch 332 generally draw the paperboard blank outof the ridge 362 and deform it into the intermediate container shape.This process also forms the pleats 289 as the flat paperboard blank isat least partially folded upon itself and pressed flat to achieve thethree-dimensional shape of the intermediate container 318. Each suchfold and pressing form a pleat 289. Further, the closing of the die set330 aligns the first die sidewall 354 with the first angled sidewall 346of the punch 332, and the second die sidewall 356 with the second angledsidewall 348. Accordingly, the intermediate container sidewall 324 iscompressed to form the ridge 325, lower sidewall 327, and upper sidewall329 at the angles previously mentioned.

The general operating conditions of the first die set 330 will now bedescribed. Between 6,000 and 25,000 pounds of force may be applied bythe first die set 330, with a more specific range of 6,000 to 15,000pounds of force. The operating temperatures of both the punch 332 anddie 334 are between 200 and 350 degrees Fahrenheit, with a more specificrange of 240 to 350 degrees Fahrenheit. The punch 332 remains closed inthe die 334 for 0.1 second to 5.0 seconds, with a preferred closuredwell time of 0.03 to 1.0 seconds. The moisture level of the paperboardblank prior to entering the die 334 can be in the range of about 8-11%,with a more specific range of about 9-9.5%.

FIG. 33 is an enlarged, fragmentary, cross-sectional view of theportions of the punch 332 and die 334 forming the downturned portion 322and perpendicular portion 326 of the intermediate container 318. Asshown in FIG. 33, the combination of upwardly angled die shoulder 358and the angled shoulder 342 cooperate to form the downturned portion 322of the intermediate container's flange 320. Similarly, as the die set330 closes, a portion of the blank is drawn into the void space betweenthe punch's edge wall 344 and the die edge wall 360 to form theperpendicular portion 326 of the intermediate container 318. Both thedownturned portion 322 and the perpendicular portion 326 of the flangerun along the entire circumference of the intermediate container 318.

Referring to FIG. 34, after the punch 332 and the die 334 cooperate toform the blank into the intermediate container 318, the die 334retracts. Simultaneously, a plunger 364 rises from the punch, holdingthe base 366 of the intermediate container 318 against the top wall 350of the die 334. An outer die ring 368 does not retract, but insteadremains at least partially in contact with the punch 332. As the die 334and the plunger 364 move, the perpendicular portion 326 of theintermediate container 318 moves. If the perpendicular portion's edgecontacts the shoulder of the ring 368, the downward force exertedagainst the intermediate container 318 may facilitate removing thecontainer from the die 334. An outer punch ring 370 moves up and down,and stays in contact with the die ring 368 until it reaches the heightof the punch surface.

Referring to FIG. 35, once the die 334 and the plunger 364 have moved tobottom out and compress the paperboard blank, the plunger 364 and punch332 retract and the intermediate container 318 moves downward, ejectingitself from the die 334. At least two factors facilitate the ejection ofthe intermediate container 318 from the die 334. First, the paperboardof the intermediate container 318 is at least somewhat naturallyresilient. This characteristic tends to force the sidewall 324 againstthe sidewall of the die 334, which in turn levers the intermediatecontainer 318 out of the die 334. Second, placing the die 334 above thepunch 332 ensures gravity acts to pull the intermediate container 318out of the die 334. Airjets or ejector pins may optionally be employedto force the intermediate container 318 out of the die 334, as describedabove with respect to a previous embodiment. These ejection assists mayalso be used to eject containers from punches in other embodiments.

FIGS. 36-39 illustrate formation of the final container 288 from theintermediate form 318. Referring to FIG. 36, once the intermediatecontainer 318 has been created from a blank, the intermediate container318 may be placed within, or otherwise transferred to, a second die set372 to form the final container 288. The second die set 372 also has adie 376 and a punch 374 located beneath the die 376. Generally, thephysical characteristics of the punch 374 and die 376 of the second dieset 372 match those of the punch 332 and die 334 of the first die set330, albeit with some exceptions as described below. Initially, theintermediate container 318 is placed upon the punch 374. Theintermediate container 318 may be slightly off-center as the secondforming process begins without affecting the process. The punch 374 alsoincludes a male protrusion 378 running circumferentially along a flat,outer plate 380 of the punch.

The die 376 is lowered onto the punch 374, with the intermediatecontainer 318 resting on the punch 374. As the punch 374 enters the die376, the container sidewall 324 contacts the die sidewall 380. As can beseen in FIGS. 36 and 37A, the die sidewall 380 is formed of a verticalsidewall segment 382 and an angled sidewall segment 384. The angledsidewall segment 384 extends at an angle of approximately 30 to 31degrees, matching the angle of the upper sidewall 329 formed in thefirst die set 330.

Referring to FIG. 37A, even when the second die set 372 is fully closed,the intermediate container 318 lower sidewall 327 does not contact thevertical sidewall segment 382 of the die 376. This permits theintermediate container 318 to enter the die 376 without impacting, orpotentially being crushed or deformed by, the die sidewall 380. In theevent the intermediate container 318 is off-center on the punch 374, theintermediate container 318 is centered as its upper sidewall 329 comesinto contact with the angled sidewall segment 384 during closure of thedie set 372. When desirable to operate the second die set 372 and firstdie set 330 simultaneously, forces applied to the first die set 330 willbe available to the second die set 372 for deformation and/or shaping ofthe intermediate container 318. The operating temperature of the seconddie set 372 may be in the range of about 200 to 350 degrees Fahrenheit,with the punch 374 having an operating temperature of about 200-355degrees and the die 376 having an operating temperature of 240 to 325degrees.

When the first die set 330 and second die set 372 are interlinked andsimultaneously operate, an additional force may be applied to the seconddie set 372 during closure in order to equalize the closing force of thefirst die set 330. The equalizing force may ensure the die sets 330, 372close substantially simultaneously, and prevent either die set fromcocking or closing unevenly. Thus, the equalizing force may furtherprevent uneven pressing of a paperboard blank or container in either dieset.

Once the die 376 completely receives the punch 374, stabilizing,centering, and immobilizing the intermediate container 318 therebetween,a circular flange formation element 386 is lowered. FIG. 36 shows theflange formation element 386 retracted from the die 376, so that thebottom surface of the flange formation element 386 is higher than thelower surface of the die 376. FIG. 37A shows the flange formationelement 386 lowered around the die, so that the bottom surface of theflange formation element 386 is lower than the bottom surface of the die376. The flange formation element 386 is generally continuous andencircles the entirety of the die 376.

Referring to FIG. 37A, the flange formation element 386 includes aformation sidewall 388, sloping inwardly to a formation cavity 390. Theformation cavity 390 is bounded on its inner edge (the edge closest tothe die 376) by a formation shoulder 392. As the flange formationelement 386 descends around the die 376, the distal edge of thecontainer perpendicular portion 326 impacts the formation sidewall 388.Upon initial impact, and after the intermediate container 318 centers onthe punch 374, the downturned portion 322 of the intermediate container318 is held against the outer plate 380 by a lip 394 of the die 376.This prevents the downturned portion 322 from moving when the distaledge of the perpendicular portion 326 impacts the formation sidewall388.

FIG. 37B is an enlarged view of the protrusion 378 and the flangeformation element 386 in a partially-open state. The formation cavity390 (measured from the end to the point at which the formation cavityimpacts the outer plate 380) is larger than the protrusion 378. Theformation sidewall 388 has a 20 degree slope. The outer ring 380 may bedivided into an inner ring portion 381 and outer ring portion 383, eachon a different side of the protrusion 378. The protrusion 378 is 0.05inches wide. The formation cavity 390 has a radial width of 0.145inches. The protrusion 378 is approximately 0.035 inches high, while theformation cavity 390 is approximately 0.0507 inches deep. Thesedimensions may vary, for example, in alternate embodiments. The elements381 and 383 lie in a flat, horizontal plane. However, they may bedeformed at a slight angle to create the finished flange.

Returning to FIG. 37A, the formation sidewall 388 is sloped inwardly,towards the die 376, at an approximate 20 degree angle. The flangeformation element's downward motion rolls the distal edge of theperpendicular portion 326 inward, towards the die 376 and punch 374 andinto the formation cavity 390. Since the paperboard is at least somewhatflexible, it rolls rather than crumples. This flexibility is aided byenhancing the paperboard moisture, raising it to between about 2% to13%, or more specifically between about 8% and 10% by weight. Therolling of the perpendicular portion 326 forms the rolled portion 304 ofthe finished flange 290. The formation shoulder 392 bounds the formationcavity 390, and ensures the perpendicular portion 326 does not extendtoo far towards the die 376 as the formation element 386 closes.

In addition to rolling the perpendicular portion 326, the flangeformation element 386 generally presses the downturned portion 322 ofthe intermediate container 318 against the outer plate 380 of the punch374. As the formation element 386 lowers and the perpendicular portion326 is forced under the downturned portion 322 (see FIG. 37A), a forceis also vectored parallel to the outer plate's surface. Thus, two forcevectors act upon the downturned portion: a first force vector pressesthe downturned portion 322 against the outer plate 380 and perpendicularto the circumferential protrusion 378, while a second force vectorpresses the downturned portion 322 laterally to the outer plate 380 andagainst an outer edge of the protrusion 378.

The combination of forces causes the downturned portion 322 to “wrap”around the protrusion 378, conforming thereto. Thus, even though theformation cavity 390 is substantially larger than the protrusion 378 andlacks a completely complementary female surface, the downturned portion322 nonetheless is pressed fully about the protrusion 378. This is dueto two paperboard/film thicknesses equal to 0.036 inches beingcompressed into a closed gap of 0.030-0.033 inches. Alternateembodiments may have different measurements for the gap orpaperboard/film material. The formation shoulder 392, in combinationwith the now-rolled perpendicular portion 326, forces the inner sectionof the container's downturned portion 322 against the inner edge of theprotrusion 378. When the formation element 386 is completely loweredabout the die 376, the now-rolled perpendicular portion 326 occupiessubstantially all available area between the inner edge of theprotrusion 378 and the formation shoulder 392. This prevents thedownturned portion 322 of the intermediate container 318 from bucklingupwardly and into the formation cavity 390. The resulting forces createthe aforementioned “wrapping” effect, conforming the downturned portionto the profile of the protrusion 378. This forms the depression/groove294 described above with reference to FIGS. 28-30.

The relatively small space in the formation cavity 390, coupled with thepressure applied to the section of the downturned portion 322 wrappedaround the male protrusion 378 to form the top, flat portion of thefinished flange (i.e., outer wall of the depression 304 of the finishedcontainer 288), deforms the perpendicular portion 326. This deformationresists decoupling or expansion of the flange 290 in the final, formedcontainer 288 and additionally may impart structural strength to thecontainer 288. Additionally, the pressure substantially straightens thedownturned portion 322, so that the finished flange 372 is essentiallyparallel to the bottom surface of the container 288, and sufficientlydeforms the paperboard to minimize springback or unrolling of thefinished flange 372.

The perpendicular portion 326 of the container 288 may also be bonded tothe downturned portion 322 by the aforementioned combination of pressureand small space in some embodiments. FIG. 37C is an enlarged view of theprotrusion 378 and formation cavity 390, with the die set 372 closed.The paperboard 391 shown in the formation cavity 390 may beapproximately 0.017 inches thick, while the film laminated thereto maybe approximately 0.005 inches thick. As shown in FIG. 37G. thepaperboard 390 does not roll under the entirety of the paperboardwrapped around the protrusion 378, but instead typically terminates at apoint approximately three-quarters along the protrusion 378.

FIG. 37D is a detailed view of the flange formation element 386,including several exemplary measurements. Alternate embodiments mayemploy different dimensions without departing from the spirit or scopeof the present invention. In FIG. 37D, d1=0.0592 in., d2=0.0858 in.,d3=0.0507 in., d4=0.4064 in., d5=0.2334 in., d6=0.4527 in., d7=0.7207in., r1=0.0622 in., r2=0.0975 in., α1=30 degrees, and α2=29 degrees.

Referring to FIG. 38, after the perpendicular portion 326 is rolled intothe formation cavity 390 and the downturned portion 322 is molded aroundthe protrusion 378, the flange formation element 386 is withdrawn.

Next, as shown in cross-section in FIG. 39, the die 376 is withdrawn.The final, formed container 288 may be withdrawn from the second die set372. An air-assist or ejector pin may be used to facilitate removal ofthe container 288.

The aforementioned manufacturing process for forming a container 288having a rolled flange 290 with a depression 294 formed therein has beendescribed as a two-stage process. The first and second die sets 330, 372may be part of a single apparatus, or may be separate from one another.Further, the first and second die sets may be interlinked such that bothdie sets 330, 372 close and open on the same motion. If the die sets330, 372 are mounted on an inclined surface, gravity (optionally with anair-assist or ejector pin) may be used to transfer containers 288between the first and second die sets 330, 372. Optionally, a chute,conveyor belt, or other mechanism may convey the intermediate container318 from the first die set 330 to the second die set 372 for furtherforming. The conveyor belt may be, for example, a vacuum belt.Additionally, in some embodiments, the second die set 372 may be omittedand the depression 294 formed in the first die set 330.

The forming methods discussed in detail above with reference to FIGS.26-39 allow containers 288 to be produced having a substantially uniformouter diameter across the entire circumference of the container 288.Similarly, the thickness of the flange 290, as established by the radiusof the rolled portion 304, is also substantially uniform. The flange topsurface 293 and rolled portion 304 thickness may also be substantiallyuniform. Further, these elements are of substantially the samedimensions from one container 288 to another. For example, the thicknessand outer diameter of the flange 290 may vary by no more than 5/1000thsto 8/1000ths of an inch between containers. The extent to which therolled portion 304 underlies the depression 294, however, may vary alongthe flange 290 and container 288 circumference.

Because each container 288 has a flange 290 of relatively uniform outerdiameter and thickness, the containers 288 may be reliably lidded withsnap-fit lids of appropriate size. The use of snap-fit lids isfacilitated by uniform containers 288 because snap-fit lids generallyrequire strict tolerances in order to achieve a proper fit. By contrast,containers of conventional construction may have flange outer diametersor thicknesses that vary too greatly from one container to another,rendering snap-fit lids inappropriate. In alternative embodiments, ametal lid may be mechanically rolled onto or otherwise attached to thecontainer 288.

Similarly, a film may be heat-sealed to the flange 290 to create a lid.Because the flange 290 is uniform in its outer diameter and thickness(i.e., is “dimensionally stable”), a film may be created in a standardsize for heat-sealing to the flange 290. Further, the dimensionalstability of the flange 290 minimizes any gapping or discontinuitybetween the film and flange top surface 293, in turn minimizing airflowpaths between the interior of a sealed container 288 and the atmosphere.

The general shape of the flange 290 may be varied by modifying thecross-sectional profile of the formation cavity 390, the formationsidewall 388, and/or the formation shoulder 392. For example, FIG. 40 isan enlarged, fragmentary cross-sectional view of a seventh embodiment ofa flange 396 incorporated into a nestable container 398, similar to thecontainer 288 section shown in FIG. 30. The flange 396 includes adepression 400 formed therein and a rolled portion 402, as discussedpreviously with respect to FIGS. 28-30. In the container 398, however,the rolled portion 402 forms an offset 404 perpendicular with respect toa top surface 401 of the flange 396. The thickness of the rolled portion402 increases at the offset 404, and the offset 404 thereby providesadditional space between nested containers 398, and thus may enhancedenestability in some applications. The rolled portion 402 may extendunderneath the depression 400 to form an extending under-segment 406,after forming the offset 404. A peripheral edge 405 of the flange 396may be curved to facilitate denesting.

The thickness of the offset 404 and the under-segment 406 exceeds thatof the outer section of the rolled portion 402. Effectively, the outersection of the rolled portion 402 is compressed in a die set to narrowits thickness, while the offset 404 and under-segment 406 are not sostrongly compressed.

Yet another embodiment (not shown) may form a flange having a depressionrunning continuously along the flange top surface, as described withrespect to FIGS. 28-30, but lacking a rolled portion extendingdownwardly and underneath the depression.

Still other flange embodiments may be formed. For example, thedepression previously mentioned may be replaced with a raised surface, adimple, or a ring on the flange. That is, the raised surface may extendupwardly from the top of the flange, rather than downwardly from thebottom. Such raised surfaces may be used in combination with, or inplace of, any flange mentioned herein. As another example, a flange mayhave one or more circular depressions, dimples, or grooves, along with araised surface. The depressions and raised surfaces may alternate eitherradially or circumferentially along the flange. Yet other embodimentsmay omit such depressions, grooves, and/or raised surfaces entirely.

FIG. 41 is an isometric view, looking upwardly, of an eighth flangeembodiment forming part of a container. Here, a flange 408 includes aseries of depending square edges 410. The square edges 410 occurapproximately at intermittent angles β around the circumference of theflange. The angle β may be, in one embodiment, a fifteen degree arc. Thearc between square edges 410, and the arc occupied by each square edge410, may vary. In the present embodiment, the square edges 410 may havea radial width of approximately 0.035 inches, and a thickness ofapproximately 0.035 inches. These square edges 410 formed on the flange408 permit denesting in the manner previously described, as well asproviding an increase in flange strength and facilitating the use ofvarious lids. It should be noted the portions of the flange 408 in theintermediate arc segments 412 between square edges 410 may be rolled,deformed, or compressed to maintain a constant outer diameter for theassociated container.

FIGS. 42-49 illustrate a ninth embodiment of a pressed container 500 anda method of making the container 500. The container 500 has the shape ofa plate and includes a flange 510 extending outwardly from the entiretyof the container sidewall 512. A depression or groove 514 can be formedin the flange 510 spaced from the flange's top surface 513 from thejoinder of the flange 510 and sidewall 512. The groove 514 runs alongthe circumference of the flange 510, and is generally U-shaped incross-section, as seen in FIG. 43. The groove 514 can be any depth orconfiguration as desired, including those specified in the aboveembodiments. The top surface 513 can include a flat section 515 betweenan upper sidewall 516 and the groove 514. The flange 510 can alsoinclude any turn down, rolling, or folding as desired, including thosedetailed in the embodiments shown above. The flange 510 is shown inFIGS. 42-49 with the optional flat section 515, groove 514, and angledupper sidewall 516. The flange 510 is shown in FIG. 42 divided into aninner flange segment 506 and outer flange segment 508 by the depression514. Alternate embodiments can vary the placement of the depression 514on the surface of the flange 510, the depression thickness or width,and/or the overall flange dimensions.

As also shown in FIG. 42, the sidewall 512 is divided into an uppersidewall 516 and a lower sidewall 518. The upper sidewall 516 and lowersidewall 518 extend at different angles relative to the container base520, and meet at a ridge 502. The ridge 502 marks the change in anglefrom the sharper or steeper angle of the lower sidewall 518 to thegentler angle of the upper sidewall 516. When measured with respect to aplane perpendicular to the base 520, the interior of the lower sidewall518 preferably forms an angle of approximately 19 degrees, while theupper sidewall preferably forms an angle of approximately 30 degrees.These angles generally permit a certain amount of lateral motion (i.e.,motion in the X or Y planes) to occur when multiple containers arestacked, but can inhibit large amounts of such motion. Further, suchangles facilitate stacking containers 500 in such a manner that theflanges 510 of adjacent containers 500 abut one another, rather than thesidewalls 512 of adjacent containers 500. The 19-degree angle of thelower sidewall 518 can enable self-alignment of stacked containers,permitting the outer diameters of each container 500 to align in aheight dimension. Different embodiments may use different angles for theupper 516 and lower sidewalls 518. For example, containers of differingflange thickness, diameters, or depths may employ different angularmeasurements for the sidewalls.

The container 500 typically also has multiple pleats 519 radiallyextending from the container's bottom surface 520 along the sidewall512. These pleats 519 are similar to those discussed in more detailabove with reference to FIG. 1. Approximately 40 to 80 pleats arepresent on each blank, with 60 to 72 pleats preferred in a five-inchouter-diameter container and more in a nine-inch diameter plate. Theexact number of pleats employed in an embodiment varies with the outerdiameter, depth, and shape of the container.

As shown in FIG. 42, the flange 510 has a substantially uniform outerdiameter across the entire circumference of the container 500, and asubstantially uniform flange thickness, as established by the radius ofthe rolled portion 504. Also, the flange top surface 513 and the rolledportion 504 thickness are substantially uniform. In the presentembodiment, the thickness and the outer diameter of the flange 510 donot vary, or vary only to a minor degree, between containers, so thatthe container 500 is substantially reproducible. The extent to which therolled portion 504 underlies the depression 514, however, can vary alongthe flange and container 500 circumferences.

Because each container 500 has a flange 510 of relatively uniform outerdiameter and thickness, the containers 500 may be lidded with a snap-fitlid. The relatively uniform dimensions and the attendant reproducibilityof the container 500 allow for the use of snap-fit lids, which haverelatively tight size tolerances. In other embodiments, a plastic lidcan be affixed to the flange 510 and the groove 514 can help seal thelids to the plates, containers, bowls, or other formation.

Similarly, a film may be heat-sealed to the flange 510 to create a lid.Because the flange 510 is uniform in its outer diameter and thickness(i.e., is “dimensionally stable”), a film may be created in a standardsize for heat-sealing to the flange 510. Further, the dimensionalstability of the flange 510 minimizes any gapping or discontinuitybetween the film and flange top surface 513, in turn minimizing airflowpaths between the interior of a sealed container 500 and the atmosphere.

FIG. 43 is a cross-sectional view of a pressed container 500, takenalong line 43-43 of FIG. 42. This view shows the ridge 502 and the anglebetween the upper sidewall 516 and lower sidewall 518, as well as across-section of the flange 510.

With respect to the angled sidewall 512, the ridge 502 defining thechange in angles between the lower sidewall 518 and upper sidewall 516adds multiple benefits to the container 500. First, the ridge 502 mayimpart additional structural strength to the container 500. The ridge502 resists twisting and/or shear stresses applied perpendicular to thebottom surface 520, minimizing deformation that may result therefrom.This may be referred to as the “hoop strength” of the container 500. Forexample, the increased hoop strength of the container 500 may enhancethe angled sidewall's 512 resistance to pressure applied by a series ofstacked, nested containers. Thus, the ridge 502 may prevent deformationthat would otherwise occur in a container.

FIG. 44 is an enlarged, fragmentary, cross-sectional view of the flange510 and the upper sidewall 516. A portion 504 of the flange 510 rollsunderneath the flange top surface 513 and at least partially beneath thegroove 514. The rolled portion 504 extends from the flange's outer rim505 under the outer segment 508, and along the under-surface 524 of thedepression 514. Typically, the rolled portion 504 extends entirely alongthe depression's circumference, along under-surface 524, and continuesalong the under-surface 525 of the flat section 515 of the top surface513 of the flange 510. This distance of extension can change inalternate embodiments and incorporates at least those variations asshown in the present disclosure. For example, in some embodiments therolled portion 504 can extend along approximately 40% to 75% of thedepression's circumference before terminating. The rolled portion 504generally increases the thickness of the flange 510 and, in combinationwith or in addition to the grooves 514 formed therein, aid in theremoval of container 500 from a stack. Further, the grooves of theflanges 510 can help seal plastic lids to the containers 500 as desired.

An inner surface 522 of the rolled portion 504 abuts the under-surface524 of the depression 514. During formation of the container 500, theinner surface 522 and under-surface 524 can be pressure bonded to oneanother, which can, for example, create a cross-linking of fibersbetween these paperboard layers. The pressure bond generally assists inmaintaining the curvature of the rolled portion 504 by maintainingcontact between the rolled portion's inner surface 522 and thedepression's under-surface 524. This, in turn, prevents the flange 510from deforming with time or use. Regardless of whether such pressurebonding occurs, the rolled portion 504 is deformed to assume the shapegenerally shown in FIG. 43, and the deformation increases the flangethickness and can assist in, for example, sealing the container 500 to aplastic lid applied thereto. In FIG. 44, by way of example, the angle γcan have a value of 30 degrees, and ρ can have a value of 19 degrees.

The inner surface 522 of the rolled portion 504 and the underside of theouter segment 508 define a void space 526. The void space 526 generallyincreases the overall thickness of the flange 510.

Referring to FIG. 45, the ridges 502 of multiple stacked containers 500generally do not abut one another. Specifically, when a first container500 is nested or stacked within a second container 500, the outersurface of the first container's ridge 502 does not abut the innersurface of the second container's ridge 502. Rather, the preferrednested containers 500 contact one another at the flanges 510. Thisprovides lateral stability for a stack of containers 500, permittingcontainers to self-align and thus facilitating denesting.

As shown in FIG. 44, the flange 510 extends downwardly at an anglebetween 1 degree to 89 degrees from the top surface 513. This downwardshape of the flange 510 in the present embodiment provides an additionalresistance to bending and other deformations. Thus, in this embodiment,the shape of the flange 510 provides containers 500 of consistent anduniform outside diameters, which are perceived to be stronger andthicker in general since the shape of the flange 510 helps resistbending and other deformation. In alternate embodiments, the featuresshown in FIG. 44 can mostly be used in the alternative. However, inthese alternate embodiments, the flanges should be folded under at leastpartially and should extend downward at an angle. All other elementswould optionally be used in varying embodiments with the folded under,angled flange providing enough strength and thickness to impartstrength, providing denesting ability, and providing a seal for plasticor other lids to be applied to the plate or container. Thus, thereproducibility of the flange 510 of the container 500 in the presentembodiment allows for consistent and uniform outside diameters ofcontainers to be maintained to enable sealing of plastic or other lidsto the plates or containers.

As also shown in FIG. 44, the flange 510 and the upper sidewall 516 meetin a circumferential curved edge 534, rather than forming an angledjunction. The curved edge 534 may have a radius of approximately 0.045inches, although this dimension can vary in alternate embodiments. Thecurved edge 534 facilitates a gradual change in angle between flange 510and upper sidewall 516, as well as denesting operations. In someembodiments, the curved edge may be replaced by a more abrupt, angledtransition.

The outer edge of the flange 510 generally defines an angled peripheraledge 505 between the outer flange segment 508 and the rolled portion504. When multiple containers 500 are stacked or nested, the rolledportion 504 of a top container rests upon the top surface 513 of abottom container's flange 510, as shown in FIG. 45. The base of the topcontainer's rolled portion 504 can rest at least partially within thebottom container's depression 514, as shown in FIG. 43. However, theradius of the rolled portion 504 is generally greater than the radius ofthe depression 514. Thus, although the bottom container's depression 514can partially accept the base of the top container's rolled portion 504,the rolled portion 504 nonetheless extends upwardly to space the topcontainer's angled edge 505 from the bottom container's angled edge 505,and increases the overall thickness of the flange 510. As shown in FIG.45, this spacing permits a knife edge 92 of a denesting apparatus 68 tomove between adjacent containers 500, in turn allowing denesting ofcontainers 500.

FIGS. 46-51B illustrate various stages during the process ofmanufacturing the nestable container 500. As with previously describedembodiments, the present container 500 is manufactured in a two-stageprocess. The first stage is forming, from a circular blank, anintermediate container 540 having a downturned flange 542 including adownturned portion 544 adjacent to a container sidewall 546, and aperpendicular portion 548 depending from the downturned portion 544. Theprocess for manufacturing the intermediate container is generally shownin FIGS. 46-49, with the intermediate container 540 shown to best effectin FIG. 49. The finished container 500 is formed from the intermediatecontainer 540 in the second stage.

The diameter and thickness of a circular paperboard blank used to formthe intermediate container 540 are generally sized to the finalproduct's desired dimensions, with the die sets used to form thecontainer 500 dimensioned accordingly. The paperboard blank can alsoinclude a film or laminate, and may be approximately 0.0005 inchesthick. Referring to FIGS. 42-45, the container 500 may have an outsidediameter of 9 inches. A container of 9 inch outside diameter may beformed in a die set that includes an approximately 7.15 inch innercontainer diameter and approximately between 8.275 and 8.319 inches forthe die set, allowing for a container thickness of between approximately0.01 to 0.045 inches.

Referring to FIG. 46, a die set 550 for forming the intermediatecontainer 540 is shown in cross-section. The die set 550 includes aforming punch 552 seated in the forming die 554, with the blank pressedinto the intermediate container 540. The punch 552 can be located eitherabove or beneath the forming die 554, similar to either of the die sets48, 118, 154, 202, 256, or 330. The punch 552 has a frustoconicalprotrusion 556 defining a flat, circular top wall 558, a generallyfrustoconical sidewall 560, an angled shoulder 562, and an upwardlyextending edge wall 564. The frustoconical sidewall 560 is furtherdivided into a first angled sidewall portion 566 and second angledsidewall portion 568, which meet at a circumferential ridge point 571.The first and second angled sidewalls 566, 568 extend at differentangles from a plane parallel to the top wall 558. Specifically, in thepresent embodiment the first angled sidewall portion 566 formsapproximately a 19-degree angle with the top wall 558, while the secondangled sidewall portion 568 extends at approximately 30 degrees from aplane perpendicular to the top wall of the punch 552.

The angled shoulder 562 of the punch 552 angles slightly towards the topwall 558, and abuts the second angled sidewall 568. The edge wall 564extends upwardly and defines an outer shoulder. As described in moredetail below, the angled shoulder 562 and the edge wall 564 combine witha mating surface on the die 554 to form the downturned portion 544 andperpendicular portion 548 of the intermediate container 540.

The die 554 includes a flat, circular top wall 570, a generallyfrustoconical, downwardly-extending sidewall 572 composed of a first diesidewall 574 and a second die sidewall 576, an upwardly angled dieshoulder 578, and an upwardly-extending die edge wall 580. As discussedwith respect to the punch 552, the first and second die sidewalls 574,576 extend at different angles and meet at a die ridge 581 extendingalong the circumference of the die 554. The first die sidewall 574extends from the top wall 570 at approximately a 19-degree angle, whilethe second die sidewall 576 extends from the ridge at approximately a30-degree angle, measured with respect to a plane perpendicular to thetop wall 570.

FIG. 47 illustrates certain elements of the die 554 and punch 552. Toform the container 540, first, a circular blank (not shown) is insertedbetween the punch 552 and die 554, while the die set 550 is open. Theblank generally seats in the flat, circular ridge 582 atop the punch552. Once the blank is seated, the die 554 is lowered onto the punch552, bending, compressing, and deforming the paperboard blank to formthe intermediate container 540 shown in FIG. 46. As the die set 550closes, the complementary surfaces of the die 554 and the punch 552generally draw the paperboard blank out of the ridge 582 and deform itinto the intermediate container shape. This process also forms thepleats 519 mentioned above, insofar as the flat paperboard blank is atleast partially folded upon itself and pressed flat to achieve thethree-dimensional shape of the intermediate container 540. Each suchfold and pressing form a pleat 519. Further, the closing of the die set550 aligns the first die sidewall 574 with the first angled sidewall 566of the punch 552, and the second die sidewall 576 with the second angledsidewall 568. Accordingly, the intermediate container sidewall 546 iscompressed to form a ridge 545, a lower sidewall 547, and an uppersidewall 549 at the angles described above.

The general operating conditions of the die set 550 operate at or aroundthe temperatures and force ranges of the die sets described in otherembodiments detailed in the disclosure herein. The moisture content inthe paperboard blank may also be in the same range as the embodimentsdiscussed herein.

FIG. 47 is an enlarged, fragmentary, cross-sectional view of theportions of the punch 552 and die 554 forming the downturned portion 544and perpendicular portion 548 of the intermediate container 540. Asshown in FIG. 47, the combination of upwardly angled die shoulder 578and angled shoulder 562 cooperate to form the downturned portion 544 ofthe intermediate container's flange 542. Similarly, as the die set 550closes, a portion of the blank is drawn into the void space between thepunch's edge wall 564 and the die edge wall 580 to form theperpendicular portion 548 of the intermediate container 540. Both thedownturned portion 544 and the perpendicular portion 548 of the flange542 run along the entire circumference of the intermediate container540.

After the punch 552 and the die 554 cooperate to form the blank into theintermediate container 540, the die 554 retracts. This operation isgenerally shown in the cross-sectional view of FIG. 48. Simultaneously,a plunger 584 rises from the punch, holding the base 586 of theintermediate container form 540 against the top wall 570 of the die. Anouter punch ring 588 does not retract, but instead remains at leastpartially in contact with the punch 552.

As the die 554 and plunger 584 move, the perpendicular portion 548 ofthe container 540 moves. If the perpendicular portion's edge contactsthe shoulder of the outer punch ring 588, the downward force exertedagainst the container 540 may facilitate removing the container from thedie 554.

Once the die 554 and plunger 584 have moved to bottom out and compressthe paperboard blank, the plunger 584 and the punch 552 retract and theintermediate container 540 moves downward, ejecting itself from the die554, as shown in the cross-sectional view of FIG. 49. At least twofactors facilitate the ejection of the intermediate container 540 fromthe die 554. First, the paperboard of intermediate container 540 is atleast somewhat naturally resilient. This tends to force the sidewall 546against the sidewall of the die 554, which in turn levers theintermediate container 540 out of the die. Second, placing the die 554above the punch 552 (i.e., upside-down with respect to conventionalpunch-and-die placement) ensures gravity acts to pull the intermediatecontainer form 540 out of the die 554. Airjets or ejector pins mayoptionally be employed to force the container form 540 out of the die554, as described above with respect to previous die embodiments. Theseejection assists may also be used to eject the intermediate containerforms from the punches used in other embodiments.

FIGS. 50-51C illustrate a second stage of manufacturing the container500. Referring to FIG. 50, after forming the intermediate container form540, the intermediate container 540 may be placed within, or otherwisetransferred to, a second die set 590 to form the final container 500.The second die set 590 also has a punch 592 and a die 594, with thepunch 592 being located beneath the die 594. The punch 592 includes amale protrusion 596 running circumferentially along a flat, outercontainer 598 of the punch 592, with the intermediate container form 540being placed on the punch 592 in FIG. 50. The physical characteristicsof the punch 592 and die 594 of the second die set 590 may generallymatch those of the punch 552 and die 554 of the first die set 550,albeit with some structural variations described below.

The punch 592 is raised into the die 594, with the intermediatecontainer form 540 resting on the punch 592. As the punch 592 enters thedie 594, the container sidewall 546 contacts the die sidewall 598. Ascan be seen in FIGS. 50 and 51A, the die sidewall 598 is formed of avertical sidewall segment 600 and an angled sidewall segment 602. Theangled sidewall segment 602 extends at an angle of approximately 30degrees, matching the angle of the upper sidewall formed in the firstdie set 550.

FIG. 51A shows the die set 590 when fully closed on the intermediatecontainer form 540. Even when the second die set 590 is fully closed,the intermediate container form's lower sidewall 547 does not contactthe vertical sidewall segment 600 of the die 594. This permits thecontainer to enter the die 594 without impacting, or potentially beingcrushed or deformed by, the die sidewall. In the event the intermediatecontainer form 540 is off-center on the punch 592, the intermediatecontainer form 540 is centered as its upper sidewall 549 comes intocontact with the angled sidewall segment 602 of the die 594 duringclosure of the die set 590. When desirable to operate the second die set590 and the first die set 550 simultaneously, forces applied to thefirst die set 550 will be available to the second die set 590 fordeformation and/or shaping of the container. Suitable operatingtemperature ranges of the second die set 590, including the punch 594and the die 592, may be analogous to other embodiments described above.

When the first die set 550 and the second die set 590 are interlinkedand operate simultaneously, an additional force may be applied to thesecond die set 590 during closure thereof, in order to equalize theclosing force of the first die set 550. The equalizing force may ensurethe die sets 550, 590 close substantially simultaneously, and preventeither die set from cocking or closing unevenly. Thus, the equalizingforce may further prevent uneven pressing of a paperboard blank orcontainer in either die set.

Once the punch 592 completely enters the die 594, stabilizing,centering, and immobilizing the intermediate container form 540therebetween, a circular flange formation element 604 is lowered. FIG.50 depicts the flange formation element 604 retracted from the die 594,with the bottom surface of the formation element 604 being higher thanthe lower surface of the die, while FIG. 51A depicts the formationelement 604 lowered around the die 594, with the bottom surface of theformation element 604 being lower than the bottom surface of the die594. The flange formation element 604 is generally continuous andencircles the entirety of the die 594.

The flange formation element 604 includes a formation sidewall 606,sloping inwardly to a formation cavity 608. The formation cavity 608 isbounded on its inner edge (the edge closest to the die 594) by aformation shoulder 610. As the flange formation element 604 descendsaround the die 594, the distal edge of the container perpendicularportion 548 impacts the formation sidewall 606. Upon initial impact, andafter the intermediate container form 540 centers on the punch 592, thedownturned portion 544 of the intermediate container is held against theouter container 598 by a lip 612 of the die 594, as shown in FIG. 51A.This prevents the downturned portion 544 from moving when the distaledge of the perpendicular portion 548 impacts the formation sidewall606.

FIG. 51B is an enlarged view of the protrusion 596 and the flangeformation element 604 in a partially open state. As shown, the formationcavity 608 (measured from the end to the point at which the formationcavity 608 impacts the outer container 598) is larger than theprotrusion 596. The formation sidewall 606 has a 20-degree slope. Theouter ring 598 may be divided into an inner ring portion 599 and outerring portion 601, each on a different side of the protrusion 596. Theprotrusion 596 is approximately 0.05 to 0.062 inches wide. The flatsection is shown as 0.075 inches wide. The protrusion 596 isapproximately 0.015 to 0.035 inches high, while the formation cavity 608is approximately 0.0538 inches deep. These measurements may vary inalternate embodiments. The elements 381, 278, and 383 lie in a flat,horizontal plane. However, they may be deformed at a slight angle tocreate the finished flange.

As shown in FIGS. 51A and 51C, the formation sidewall 606 is slopedinwardly, towards the die 594, at an approximate 20 degree angle. Theflange formation element's 604 downward motion rolls the distal edge ofthe perpendicular portion 548 inward, towards the die 594 and punch 592and into the formation cavity 608. Since the paperboard is at leastsomewhat flexible, it rolls rather than crumples. This flexibility isaided by enhancing the paperboard moisture, raising it to, for example,about 8% to 10% by weight. The overall moisture content of thepaperboard may be in the range of about 2% to 13%, or more particularlyin the range of about 8% to 10%. The rolling of the perpendicularportion 548 forms the rolled portion 504 of the finished flange 510. Theformation shoulder 610 bounds the formation cavity 608, and ensures theperpendicular portion 548 does not extend too far towards the die 594 asthe formation element 604 closes.

In addition to rolling the perpendicular portion 548, the flangeformation element 604 generally presses the downturned portion 544 ofthe intermediate container form 540 against the outer container 598 ofthe punch 592. As the formation element 608 lowers and the perpendicularportion 548 is forced under the downturned portion 544 (see FIG. 51A), aforce is also vectored parallel to the outer container's surface. Thus,two force vectors act upon the downturned portion 544: a first forcevector presses the downturned portion 544 against the outer container598 and perpendicular to the circumferential protrusion 596, while asecond force vector presses the downturned portion 544 laterally to theouter container 598 and against an outer edge of the protrusion. Thecombination of forces causes the downturned portion 544 to “wrap” aroundthe protrusion 596, conforming thereto. Thus, even though the formationcavity 608 is substantially larger than the protrusion 596 and lacks acompletely complementary female surface, the downturned portion 544nonetheless is pressed fully about the protrusion. This is due to twopaperboard/film thickness of approximately 0.036 inches being compressedinto a closed gap of 0.030-0.033 inches. Alternate embodiments may havedifferent measurements for the gap or paperboard/film material.

The formation shoulder 610, in combination with the now-rolledperpendicular portion 548, forces the inner section of the container'sdownturned portion 544 against the inner edge of the protrusion 596.When the formation element 604 is completely lowered about the die 594,the now-rolled perpendicular portion 548 occupies substantially allavailable area between the inner edge of the protrusion 596 and theformation shoulder 610. This prevents the downturned portion 544 of theintermediate container form 540 from buckling upwardly and into theformation cavity 608. The resulting forces create the aforementioned“wrapping” effect, conforming the downturned portion 544 to the profileof the protrusion 596. This forms the depression/groove 514 describedabove with respect to FIGS. 42-44.

The relatively small space in the formation cavity 608, coupled with thepressure applied to the section of the downturned portion 544 wrappedaround the male protrusion 596 to form the top, flat portion of thefinished flange (i.e., the outer wall of the depression 504 of thefinished container 500), deforms the perpendicular portion 548. Thisdeformation resists decoupling or expansion of the flange 510 in thefinal, formed container 500 and additionally may impart structuralstrength to the container 500. Additionally, the pressure substantiallystraightens the downturned portion 544, so that the finished flange 510is essentially parallel to the bottom surface of the container 500, andsufficiently deforms the paperboard to minimize springback or unrollingof the finished flange 510. The perpendicular portion 548 may also bebonded to the downturned portion 544 by the aforementioned combinationof pressure and small space in some embodiments. FIG. 51C depicts anenlarged view of the protrusion 596 and formation cavity 608, with thedie set 590 closed. In FIG. 51C, the cavity 608 extends approximately0.078 Rad. until reaching formation element 604, which extends at 0.093Rad. to mesh with protrusion 596, which extends at 0.031 Rad. By way ofexample, in FIG. 51C, A1=0.075 in., A2=0.062 in., β1=0.078 Rad.,β2=0.093 Rad., β3=0.031 Rad., β4=30 deg., and β5=20 deg.

Throughout FIGS. 42-51, the dimensions shown are exemplary. Alternateembodiments may employ different dimensions without departing from thespirit or scope of the present invention. Thus, different sizedcontainers, having the form of, for example, plates or trays, may havedifferent dimensions. The method of forming the container 500 describedabove produces containers 500 of substantially uniform shape anddimension, increasing container denestability and reproducibility. Thefinished outer diameters of the containers 500, for example, can besubstantially equal and can include additional strength enhancingfeatures, such as grooves and can accommodate lids or other attachmentsto seal the interior of the container.

The aforementioned manufacturing process for a container 500 has beendescribed as a two-stage process. Accordingly, a first die set 550 andsecond die set 590 have been discussed. In the process, the first andsecond die sets 550, 590 may be part of a single apparatus, or may beseparate from one another. Further, the first and second die sets may beinterlinked such that both die sets close and open on the same motion.If the die sets 550, 590 are mounted on an inclined surface, gravity(optionally with an air-assist or ejector pin) may be used to transfercontainers 500 between the first and second die sets 550, 590.Optionally, a chute, conveyor belt, or other mechanism may convey theintermediate container form 540 from the first die set 550 to the seconddie set 590 for further forming. The conveyor belt may be, for example,a vacuum belt.

The plates described herein, such as those shown in FIGS. 42-51, can beused in a variety of applications, including home/take out containers.

FIGS. 52A-52C illustrate a tenth embodiment of a pressed container 600.The container 600 includes a flange 610 extending outwardly from theentirety of the container sidewall 612. An upwardly concave groove ordepression 614 is formed in the flange 610, at a distance ofapproximately three-quarters of the width of the flange's top surface616 from the joinder of the flange 610 and the sidewall 612. Thedepression 614 runs along the circumference of the flange 610, and isgenerally U-shaped in cross-section. The flange 610 itself is preferablyroughly 0.3275 inches wide along its top surface 616, and divided by thedepression 614 into an inner flange segment 620 and outer flange segment622. In the illustrated embodiment, the outer diameter Φ1 of the flange610 is 4.995 inches, the inner diameter Φ2 is 4.34 inches, and theheight H1 of the container 600 is 1.078 inches. The distance L4 from thecenter of the depression 614 to the edge 624 of the flange 610 is 0.095inches, and the thickness t1 of the flange 610 is 0.090 inches.Alternate embodiments may have varying dimensions. For example, theplacement of the depression 614 on the surface of the flange 610, thedepression 614 thickness or width, and/or the overall flange dimensionsmay all vary.

Referring to FIG. 52A, the sidewall 612 may be at an angle μ of about120 degrees relative to the container base 630, or 30 degrees fromvertical. The container 600 may alternatively include two or moresidewall sections disposed at an angle to one another, as shown in FIG.29.

The container 600 typically also has multiple pleats 634 radiallyextending from the container base 630 along the sidewall 612. The pleats630 are similar to those discussed in more detail above with respect toFIG. 1. Approximately 40 to 80 score lines may be present in the blankused to form the container 600, or more particularly between 60 to 72score lines. The exact number of pleats formed in an embodiment may varywith the outer diameter, depth, and shape of the container.

A portion 640 of the flange 610 rolls underneath the flange top surface616 and at least partially beneath the depression 614. This aspect isshown in FIG. 52B, which is an enlarged, fragmentary, cross-sectionalview of the flange 610. The rolled portion 640 extends from the flange'souter rim 624 under the outer segment 622, and at least partially alongthe under-surface 650 of the depression 614. The rolled portion 640 mayextend along approximately 20% to 75% of the depression's circumferencebefore terminating, although this distance may vary in alternateembodiments. For example, in some embodiments the rolled portion 640 mayextend along the entirety of the depression's circumference. The rolledportion 640 generally increases the thickness of the flange 610. In thepresent embodiment, the flange 610 thickness is approximately 0.090inches, with a tolerance range of plus or minus 0.01 inches.

An inner surface 652 of the rolled portion 640 abuts an under-surface650 of the depression 294. During forming of the container 600, theinner surface 652 and under-surface 650 may be pressure bonded to oneanother. This may, for example, create a cross-linking of fibers betweenthese paperboard layers of the container 600. The pressure bondgenerally assists in maintaining the curvature of the rolled portion 640by maintaining contact between the rolled portion's inner surface 652and the depression's under-surface 650. This, in turn, prevents theflange 610 from deforming with time or use. The inner surface 652 of therolled portion 644 and the underside 650 of the outer segment 622 alsodefine a void space 660.

As also shown in FIG. 52C, the flange 610 and the sidewall 612 meet in acircumferential curved edge 670, which may have a radius of 0.045inches, although this dimension may change in alternate embodiments.

FIG. 52C illustrates a section of multiple containers 600. Referring toFIGS. 52B and 52C, when containers 600 are stacked, the rolled portion640 of a top container 600 rests upon the top surface 616 of a bottomcontainer's flange 610. The base of the top container's rolled portion640 may rest at least partially within the bottom container's depression614. However, the radius of the rolled portion 640 is generally greaterthan the radius of the depression 614. Thus, although the bottomcontainer's depression 614 may partially accept the base of the topcontainer's rolled portion 640, the rolled portion 640 extends upwardlyto space the top container's flange 610 from the bottom container 600.The spacing permits a knife edge of a denesting apparatus to movebetween adjacent containers 600.

FIGS. 53A-53C are sectional views illustrating an eleventh embodiment ofa container 700. The container 700 includes a flange 710 extendingoutwardly from the entirety of the container sidewall 712. An upwardlyconcave groove or depression 714, at a distance of approximatelytwo-thirds of the width of the flange's top surface 716 from the joinderof the flange 710 and a sidewall 712. The depression 714 runs along thecircumference of the flange 710, and is generally U-shaped incross-section. The flange 710 may be about 0.3275 inches wide along itstop surface 716, and divided by the depression 714 into an inner flangesegment 720 and an outer flange segment 722.

The container 700 typically also has multiple pleats 734 radiallyextending from the container base 730 along the sidewall 712. The pleats730 are similar to those discussed in more detail above with respect toFIG. 1. The exact number of pleats employed in an embodiment may varywith the outer diameter, depth, and shape of the container.

A portion 740 of the flange 710 rolls underneath the flange top surface716 and at least partially beneath the depression 714. This aspect isshown in FIG. 53B, which is an enlarged, fragmentary, cross-sectionalview of the flange 710. The rolled portion 740 extends from the flange'souter rim 724 under the outer segment 722, and at least partially alongthe under-surface 750 of the depression 714. The rolled portion 740generally increases the thickness of the flange 710. In the presentembodiment, the flange 710 thickness is approximately 0.098 inches, witha tolerance range of plus or minus 0.01 inches.

The rolled portion 740 has an undersection 742 that extends a long aradius of curvature R7, and which further extends under the depression714, so that an inner surface 752 of the rolled portion 740 may abut theunder-surface 750 of the depression 714 at one or more annularly-shapedlocations. The inner surface 752 of the rolled portion 744 and theunderside 750 of the outer segment 722 define a void space 770. Theradius R7 illustrated in FIG. 53B is about 0.128 inches, while theradius of the bottom of the depression 714 is about 0.025 inches.

FIG. 53C illustrates a section of multiple containers 700. Referring toFIGS. 53B and 53C, when containers 700 are stacked, the rolled portion740 of a top container 700 rests upon the top surface 716 of a bottomcontainer's flange 710. The base of the top container's rolled portion740 may rest at least partially within the bottom container's depression714. However, the radius of the rolled portion 740 is generally greaterthan the radius of the depression 714. Thus, although the bottomcontainer's depression 714 may partially accept the base of the topcontainer's rolled portion 740, the rolled portion 740 extends upwardlyto space the top container's flange 710 from the bottom container 700.The spacing permits a knife edge of a denesting apparatus to movebetween adjacent containers 700.

FIGS. 54A-54C are sectional views illustrating a twelfth embodiment of acontainer 800. The container 800 includes a flange 810 extendingoutwardly from the entirety of the container sidewall 812. An upwardlyconcave groove or depression 814, at a distance of approximatelythree-quarters of the width of the flange's top surface 816 from thejoinder of the flange 810 and a sidewall 812. The depression 814 runsalong the circumference of the flange 810, and is generally U-shaped incross-section. The flange 810 itself is preferably roughly 0.3285 incheswide along its top surface 816, and divided by the depression 814 intoan inner flange segment 820 and outer flange segment 822.

The container 800 typically also has multiple pleats 834 radiallyextending from the container base 830 along the sidewall 812. The pleats830 are similar to those discussed in more detail above with respect toFIG. 1. The exact number of pleats employed in an embodiment may varywith the outer diameter, depth, and shape of the container.

A portion 840 of the flange 810 rolls underneath the flange top surface816 and at least partially beneath the depression 814. This aspect isshown in FIG. 54B, which is an enlarged, fragmentary, cross-sectionalview of the flange 810. The rolled portion 840 extends from the flange'souter rim 824 under the outer segment 822, and at least partially alongthe under-surface 850 of the depression 814. The rolled portion 840generally increases the thickness of the flange 810. In the presentembodiment, the flange 810 thickness is approximately 0.073 inches, witha tolerance range of plus or minus 0.01 inches.

The rolled portion 840 extends under the depression 814 so that an innersurface 852 of the rolled portion 840 abuts the under-surface 850 of thedepression 814. The inner surface 852 contacts a bottom 854 of thegroove 814 over a distance of at least half of the width of the groove814, and may contact the groove 814 over a distance of at least threequarters of the width of the groove 814. The extended contact betweenthe under-surface 850 and the inner surface 852 increases the strengthof paper bonding between the rolled portion 840 and the under-surface850. The inner surface 852 of the rolled portion 844 and the underside850 of the outer segment 822 define a void space 860. The radius R1illustrated in FIG. 54B is 0.050 inches, while the radius of the bottomof the depression 814 is 0.034 inches.

FIG. 54C illustrates a section of multiple containers 800. Referring toFIGS. 54B and 54C, when containers 800 are stacked, the rolled portion840 of a top container 800 rests upon the top surface 816 of a bottomcontainer's flange 810. The base of the top container's rolled portion840 may rest at least partially within the bottom container's depression814. However, the radius of the rolled portion 840 is generally greaterthan the radius of the depression 814. Thus, although the bottomcontainer's depression 814 may partially accept the base of the topcontainer's rolled portion 840, the rolled portion 840 extends upwardlyto space the top container's flange 810 from the bottom container 800.The spacing permits a knife edge of a denesting apparatus to movebetween adjacent containers 800.

FIGS. 55A-55C are sectional views illustrating a thirteenth embodimentof a container 900. FIGS. 55A-55C illustrate yet another embodiment of apressed container 900. The container 900 includes a flange 910 extendingoutwardly from the entirety of the container sidewall 912. An upwardlyconcave groove or depression 914 is disposed at a distance ofapproximately three-quarters of the width of a first top surface 916from the joinder of the flange 910 and a sidewall 912. The depression914 runs along the circumference of the flange 910, and is generallyU-shaped in cross-section. The flange 910 may be about 0.3295 incheswide along its top surface 916, and divided by the depression 914 intoan inner flange segment 920 and outer flange segment 922. The container900 has multiple pleats 934 radially extending from a container base 930along the sidewall 912. The pleats 934 are similar to those discussed inmore detail above with respect to FIG. 1.

The flange 910 also includes a second top surface 918 that is offset inheight from the first top surface 916. The offset can be at least 0.1inches, and enhances the denestability of container 900.

A portion 940 of the flange 910 rolls underneath the first flange topsurface 916 and the second top surface 918, the depression 914 and thesecond flange top surface 918. This aspect is shown in FIG. 55B, whichis an enlarged, fragmentary, cross-sectional view of the flange 910. Therolled portion 940 extends from the flange's outer rim 924 under theouter segment 922, and at least partially along the under-surface 950 ofthe depression 914. The rolled portion 940 generally increases thethickness of the flange 910. In the present embodiment, the flange 910thickness is approximately 0.073 inches, with a tolerance range of plusor minus 0.01 inches.

The rolled portion 940 extends under the depression 914 so that an innersurface 952 of the rolled portion 940 abuts the under-surface 950 of thedepression 914. The inner surface 952 may contact a bottom 954 of thegroove 914 over a distance of at least half of the width of the groove914, and may further contact the groove 914 over a distance of at leastthree quarters of the width of the groove 914. The extended contactbetween the under-surface 950 and the inner surface 952 increases thestrength of paper bonding between the rolled portion 940 and theunder-surface 950. The inner surface 952 of the rolled portion 944 andthe underside 950 of the outer segment 922 define a void space 960.

FIG. 58C illustrates a section of multiple containers 900. Referring toFIGS. 55B and 55C, when containers 900 are stacked, the rolled portion940 of a top container 900 rests upon the first top surface 916 of abottom container's flange 910, without touching the second top surface918. The base of the top container's rolled portion 940 may rest atleast partially within the bottom container's depression 914. However,the radius of the rolled portion 940 is generally greater than theradius of the depression 914. Thus, although the bottom container'sdepression 914 may partially accept the base of the top container'srolled portion 940, the rolled portion 940 extends upwardly to space thetop container's flange 910 from the bottom container 900. The spacingpermits a knife edge of a denesting apparatus to move between adjacentcontainers 900.

While the containers discussed herein could be made of many differentmaterials, and while the present application has referenced specificallyan unlaminated paperboard material, many times the paperboard materialhas a moisture impervious plastic film thereon to protect the underlyingpaperboard from moisture that might be in the air, food products in thecontainer, or the like. If the upper surface of the container 242illustrated in FIG. 26, for example, has such a moisture-impervious filmthereon, the film will wrap around the top and bottom surfaces of theflange 248 so as to protect the flange 248 from moisture, which mightotherwise have a deteriorating effect on the paperboard material in theflange 248. The other embodiments discussed herein can include a similarfilm.

The containers according to the present invention may also include asingle film covering the top and bottom of the container, or twofilms—one covering the top and the other covering the bottom surface ofthe container. Additionally and/or alternatively, the containers may beclay-coated, and may optionally include an overprint coating. Generally,film laminates may be used to create a moisture-, vapor-, orgas-impervious barriers, preventing transmission of such elementsbetween a container interior and exterior, and thus potentially sealingcontainer contents. Films, for example, may prevent transmission ofoxygen, nitrogen, and/or carbon dioxide. In yet other embodiments,containers may be microwaveable, ovenable, or both (“dual-ovenable”),and may form a retortable container.

The flanges illustrated in FIGS. 24, 25, 28, 29, 40, 41-45 and 52-55 areof double thickness, which render them stronger and therefore capable ofsupporting a taller and heavier stack of containers without deforming.The flanges may also be stronger due to paper bonding of the rolledportions with upper portions of the flanges. Paper bonding in theflanges increases the stability of the resultant containers, which maybe stored in various temperatures and humidities.

In forming the abovementioned embodiments, the thickness of thepaperboard sections of the flange can be formed to any desired value.For example, FIG. 56 illustrates a section of a flange 1010 in which thethickness of paperboard sections in the flange 1010 are compressedduring forming. The flange has a depression 1014 which may be an annularring as described in the embodiments discussed above. The flange 1010includes a depression bottom 1016 having an undersurface 1050 thatcontacts an upper surface 1052 of a compressed section of a rolledportion 1040. The paperboard used to form the flange 1010 may be of aspecified caliper. During processing, the paperboard may be compressedsuch that the sum t7 of the thickness t5 and t6 may be less than about1.7 times the original caliper. In other embodiments, the thickness maybe less than 1.5 the original caliper, or even as low as 1.3 times theoriginal caliper. These thickness t7 values represent relatively highcompression of the flange 1010 because the paperboard blank used to formthe container is pleated during forming. Therefore, up to four layers ofpaperboard may be compressed to a relatively thin thickness. Highcompression of the flange 1010 sections also results in high paperbonding strength. The principles discussed with reference to FIG. 56 canbe applied to any of the flanges discussed above having rolled sections.

A variety of alternate films or laminates may be added to the variouscontainers of the present invention. For example, any of the containersdiscussed herein may be provided with a microwave susceptor layer, or aPET or CPET film. The specific films, laminations, or coatings used in agiven container may vary, depending on the intended use of thecontainer.

The denesting characteristics of the various containers described hereinrender such containers particularly suitable for a variety ofapplications, such as consumer use, food services, storage, and soforth. Further, while the embodiments disclosed herein are described anddepicted with respect to a screw denester, the embodiments may operateequally well with other forms of denesting equipment.

While circular blanks are used to make the containers discussed in thisspecification, other blank forms may be used to form differing containershapes. For example, a rectangular blank having radiused corners can beused to form a container having a rectangular shape. Another blankhaving a triangular shape with radiused corners can be used to form acontainer having a triangular shape. Such variations in blank andcontainer shape are within the scope of the invention.

In furtherance thereof and with regard to any of the afore-describedembodiments, depending upon the depth of the stack of containers thatare being denested, the weight of the stack can become significantenough to cause the flanges to flex and thereby slope radially upwardlyat the bottom of the stack. This can make it difficult for the knifeedge 92 in the denester 68 to be inserted between adjacent trays, bothbecause the opening between the flanges of adjacent trays is angledupwardly and not in alignment with the knife edge 92, and also becausethe opening becomes more narrow with an increase in the slope of theflange. To avoid the denesting problems that might be associated withlarge stacks of such containers, the flange of the containers can beformed so as to initially slope slightly downwardly and outwardly butnot so much as to prevent the knife edge from being insertedtherebetween. Therefore, as the weight of the stack increases, theflanges begin to flex upwardly but with reasonable numbers of trays in astack, the flanges would never slope upwardly and outwardly enough toinhibit a reliable relationship with the knife edge of the denester.

There are other methods for successfully stacking large numbers ofcontainers that might contain sufficient weight to flex the flange ofthe lowermost containers into a position from which they do not reliablyengage with a denester. For example, the stack could be mechanicallyseparated into smaller numbers of containers that are vertically alignedbut wherein the entire weight of the composite stack is not on thelowermost container in the stack. This approach can be accomplished, forexample, by providing additional knife edge denesters upon which aportion of the stack is supported at spaced locations along the verticalheight of the stack of containers so as to effectively divide the stackinto smaller sections of predetermined weight. In other words, there maybe one, two, or more denesting apparatuses vertically superimposed atpredetermined spaced intervals or the denesting apparatuses would nothave to necessarily be vertically superimposed but could be verticallyspaced and circumferentially displaced so as to engage the containers atdifferent locations around their perimeter.

Problems associated with the weight of a stack of containers can also bedealt with by establishing a greater gap between the flanges of adjacentcontainers. This could be accomplished by exaggerating the techniquesdescribed above for creating a gap between the flanges of adjacentcontainers.

Although the present invention has been described in the context of avariety of embodiments all taking the form of generally circular orcylindrical containers, it should be understood that the presentinvention encompasses containers of any shape, depth, flange thicknessor outer diameter, or size. For example, a square or rectangularcontainer may be manufactured with a flange having a depression runningsubstantially along the entire flange, as well as a rolled portionextending thereunder. Similarly, a square, oval, or rectangularcontainer may be manufactured with angled sidewalls as described herein.Additionally, various tolerances and relative dimensions may differ fromembodiment to embodiment. For example, one embodiment may take the formof a serving or heating tray having a relatively large (for example,nine inch) diameter and relatively short or low sidewalls. Yet anotherexample is a paper plate. Nonetheless, such a heating tray may includeany of the flange embodiments described herein, as well as theafore-discussed angled sidewalls. Accordingly, it is contemplated thatthe various features and enhancements of the present invention disclosedabove may be used with any size or shape of container, manufactured fromany suitable material.

Trays or other containers may be manufactured with two or morecompartments, for example to store different foodstuffs or other itemsin each compartment. Such containers may be provided with a flange inaccordance with the embodiments discussed herein.

The container embodiments discussed in this specification may havevarious dimensions. For example, the general container outsidediameters, heights, and sidewall angles in each container embodiment maybe applied to the other embodiments. Each container embodiment discussedherein may also be formed with two sidewall sections, as shown in FIG.42.

Although the present invention has been described with a certain degreeof particularity, it is understood the disclosure has been made by wayof example, and changes in detail or structure may be made withoutdeparting from the spirit of the invention as defined in the appendedclaims.

What is claimed is:
 1. A nestable paperboard container, comprising: abase; a sidewall attached to the base; a flange extending outwardly froman upper perimeter of the sidewall; and a denesting feature formed inthe flange, the denesting feature enhancing denestability of thecontainer; wherein the denesting feature comprises an inner peripheralportion of the flange that is adjacent to the sidewall and that isthicker than an outer portion of the flange, the thicker innerperipheral portion extending a majority of the distance around theflange.
 2. The container of claim 1, wherein the thicker innerperipheral portion extends substantially completely around the flange.3. The container of claim 1, wherein an upper peripheral area of thesidewall adjacent to the flange is thicker than a lower portion of thesidewall.
 4. The container of claim 1, wherein the flange has a width,extending radially outwardly from the sidewall, of at least ⅛ inch. 5.The container of claim 4, wherein the flange width is at least ¼ inch.6. The container of claim 1, wherein the sidewall is substantiallyfrustoconical and extends at an angle of at least 110 degrees relativeto the base.
 7. The container of claim 1, wherein the containercomprises laminated paperboard.
 8. The container of claim 1, comprisinga plurality of pleats radiating outwardly from the base.
 9. Thecontainer of claim 1, wherein the container is one of a plate or a tray.10. The container of claim 1, wherein the container is formed from asubstantially flat circular paperboard blank.